Re: [PNG] New tool to identify decode speed targets

Yeah, I was able to confirm that I was doing read buffer sizes incorrectly.

I was using FILE_STORAGE_INFO.PhysicalBytesPerSectorForPerformance
<https://learn.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_storage_info>
.
At first, I checked that I am indeed able to use any multiple of that
buffer size. Then I confirmed I can use any buffer size (including
non-multiples), even when using unbuffered IO (not using OS buffering, that
is). Then I saw in the docs that value is specifically for writes??

I meant to push a bit on this but got sick today.
I'll follow up soon. Once I can match CrystalDisk speeds on large files,
I'll feel confident it is working correctly. Right now, I'm confident it
isn't.

On Sun, Sep 28, 2025 at 10:31 AM Chris Lilley <chris@w3.org> wrote:

> I tested on my laptop, which is a couple of years old now:
>
> Dell XPS 9720, 12th Gen i9-12900HK, 64Gb DDR5 ram.
> Two SSD disks.
>
> Drive C: (1Tb NVMe PM9A1 Samsung (stock drive from Dell))
>
> PS C:\Users\chris\Documents\GitHub\FileReadSpeedTest\Test Data>
> FileReadSpeedTest '.\crystaldiskmark nvme ssd.png'
> Worker thread count: 6
> Clock is steady
> Buffer size: 512
> Open delay: 229400ns
> Open to read delay: 1009100ns
> Buffer 0 - Read issue delay: 100ns - Issue to completion delay: 142000ns
> Buffer 1 - Read issue delay: 46700ns - Issue to completion delay: 108800ns
> Buffer 2 - Read issue delay: 62900ns - Issue to completion delay: 100500ns
> Buffer 3 - Read issue delay: 75000ns - Issue to completion delay: 152500ns
> Buffer 4 - Read issue delay: 147700ns - Issue to completion delay: 93500ns
> Buffer 5 - Read issue delay: 159200ns - Issue to completion delay: 106000ns
> Buffer 6 - Read issue delay: 169600ns - Issue to completion delay: 117900ns
> Buffer 7 - Read issue delay: 180200ns - Issue to completion delay: 128900ns
> Buffer 8 - Read issue delay: 212300ns - Issue to completion delay: 226900ns
> Buffer 9 - Read issue delay: 233900ns - Issue to completion delay: 101100ns
> Buffer 10 - Read issue delay: 256300ns - Issue to completion delay:
> 113500ns
> Buffer 11 - Read issue delay: 299200ns - Issue to completion delay:
> 102400ns
> Buffer 12 - Read issue delay: 321800ns - Issue to completion delay:
> 106400ns
> Buffer 13 - Read issue delay: 332900ns - Issue to completion delay:
> 119000ns
> Buffer 14 - Read issue delay: 353500ns - Issue to completion delay:
> 117400ns
> Buffer 15 - Read issue delay: 367500ns - Issue to completion delay:
> 122200ns
> Buffer 16 - Read issue delay: 408800ns - Issue to completion delay:
> 105600ns
> Buffer 17 - Read issue delay: 433600ns - Issue to completion delay:
> 103200ns
> Buffer 18 - Read issue delay: 456100ns - Issue to completion delay:
> 101400ns
> Buffer 19 - Read issue delay: 477300ns - Issue to completion delay:
> 103200ns
> Buffer 20 - Read issue delay: 498200ns - Issue to completion delay:
> 103100ns
> Buffer 21 - Read issue delay: 508900ns - Issue to completion delay:
> 119500ns
> Buffer 22 - Read issue delay: 531200ns - Issue to completion delay:
> 118800ns
> Buffer 23 - Read issue delay: 551500ns - Issue to completion delay:
> 118600ns
> Buffer 24 - Read issue delay: 573100ns - Issue to completion delay:
> 120800ns
> Buffer 25 - Read issue delay: 593900ns - Issue to completion delay:
> 123900ns
> Buffer 26 - Read issue delay: 615200ns - Issue to completion delay:
> 181900ns
> Buffer 27 - Read issue delay: 637200ns - Issue to completion delay:
> 124500ns
> Buffer 28 - Read issue delay: 658500ns - Issue to completion delay:
> 126200ns
> Buffer 29 - Read issue delay: 679200ns - Issue to completion delay:
> 130600ns
> Buffer 30 - Read issue delay: 701900ns - Issue to completion delay:
> 128600ns
> Buffer 31 - Read issue delay: 723600ns - Issue to completion delay:
> 129100ns
> Buffer 32 - Read issue delay: 735300ns - Issue to completion delay:
> 144500ns
> Buffer 33 - Read issue delay: 758100ns - Issue to completion delay:
> 230300ns
> Buffer 34 - Read issue delay: 779600ns - Issue to completion delay:
> 141600ns
> Buffer 35 - Read issue delay: 802500ns - Issue to completion delay:
> 139800ns
> Buffer 36 - Read issue delay: 824100ns - Issue to completion delay:
> 214400ns
> Buffer 37 - Read issue delay: 844600ns - Issue to completion delay:
> 287700ns
> Buffer 38 - Read issue delay: 865300ns - Issue to completion delay:
> 147300ns
> Buffer 39 - Read issue delay: 886100ns - Issue to completion delay:
> 149400ns
> Buffer 40 - Read issue delay: 910900ns - Issue to completion delay:
> 151600ns
> Buffer 41 - Read issue delay: 932600ns - Issue to completion delay:
> 149100ns
> Buffer 42 - Read issue delay: 953000ns - Issue to completion delay:
> 152400ns
> Buffer 43 - Read issue delay: 976600ns - Issue to completion delay:
> 156600ns
> Buffer 44 - Read issue delay: 999200ns - Issue to completion delay:
> 156100ns
> Buffer 45 - Read issue delay: 1024100ns - Issue to completion delay:
> 352400ns
> Buffer 46 - Read issue delay: 1045400ns - Issue to completion delay:
> 421000ns
> Buffer 47 - Read issue delay: 1066200ns - Issue to completion delay:
> 300400ns
> Buffer 48 - Read issue delay: 1087700ns - Issue to completion delay:
> 296800ns
> Buffer 49 - Read issue delay: 1099100ns - Issue to completion delay:
> 308100ns
> Buffer 50 - Read issue delay: 1120500ns - Issue to completion delay:
> 445400ns
> Buffer 51 - Read issue delay: 1141000ns - Issue to completion delay:
> 311500ns
> Buffer 52 - Read issue delay: 1154200ns - Issue to completion delay:
> 320200ns
> Buffer 53 - Read issue delay: 1166100ns - Issue to completion delay:
> 330100ns
> Buffer 54 - Read issue delay: 1183400ns - Issue to completion delay:
> 334300ns
> Buffer 55 - Read issue delay: 1204900ns - Issue to completion delay:
> 413600ns
> Buffer 56 - Read issue delay: 1219900ns - Issue to completion delay:
> 326200ns
> Buffer 57 - Read issue delay: 1236000ns - Issue to completion delay:
> 332100ns
> Buffer 58 - Read issue delay: 1253600ns - Issue to completion delay:
> 335800ns
> Buffer 59 - Read issue delay: 1269900ns - Issue to completion delay:
> 343100ns
> Buffer 60 - Read issue delay: 1285800ns - Issue to completion delay:
> 355100ns
> Buffer 61 - Read issue delay: 1351100ns - Issue to completion delay:
> 313600ns
> Buffer 62 - Read issue delay: 1371300ns - Issue to completion delay:
> 311600ns
> Buffer 63 - Read issue delay: 1382400ns - Issue to completion delay:
> 323800ns
> Buffer 64 - Read issue delay: 1400500ns - Issue to completion delay:
> 332800ns
> Buffer 65 - Read issue delay: 1419600ns - Issue to completion delay:
> 337500ns
> Buffer 66 - Read issue delay: 1438200ns - Issue to completion delay:
> 340900ns
> Buffer 67 - Read issue delay: 1460600ns - Issue to completion delay:
> 358600ns
> Buffer 68 - Read issue delay: 1470800ns - Issue to completion delay:
> 347100ns
> Buffer 69 - Read issue delay: 1489000ns - Issue to completion delay:
> 343600ns
> Buffer 70 - Read issue delay: 1507100ns - Issue to completion delay:
> 357600ns
> Buffer 71 - Read issue delay: 1534100ns - Issue to completion delay:
> 349400ns
> Buffer 72 - Read issue delay: 1553200ns - Issue to completion delay:
> 84400ns
> Buffer 73 - Read issue delay: 1563600ns - Issue to completion delay:
> 172800ns
> Buffer 74 - Read issue delay: 1582300ns - Issue to completion delay:
> 108200ns
> Buffer 75 - Read issue delay: 1600700ns - Issue to completion delay:
> 110900ns
> Buffer 76 - Read issue delay: 1610200ns - Issue to completion delay:
> 116100ns
> Buffer 77 - Read issue delay: 1633900ns - Issue to completion delay:
> 110500ns
> Buffer 78 - Read issue delay: 1672400ns - Issue to completion delay:
> 101600ns
> Buffer 79 - Read issue delay: 1698600ns - Issue to completion delay:
> 95600ns
> Buffer 80 - Read issue delay: 1723600ns - Issue to completion delay:
> 122200ns
> Buffer 81 - Read issue delay: 1762500ns - Issue to completion delay:
> 94400ns
> Buffer 82 - Read issue delay: 1787300ns - Issue to completion delay:
> 99900ns
> Buffer 83 - Read issue delay: 1810200ns - Issue to completion delay:
> 102900ns
> Buffer 84 - Read issue delay: 1828300ns - Issue to completion delay:
> 95400ns
> Buffer 85 - Read issue delay: 1854200ns - Issue to completion delay:
> 93000ns
> Buffer 86 - Read issue delay: 1878400ns - Issue to completion delay:
> 88200ns
> Buffer 87 - Read issue delay: 1897100ns - Issue to completion delay:
> 100200ns
> Buffer 88 - Read issue delay: 1914900ns - Issue to completion delay:
> 101800ns
> Buffer 89 - Read issue delay: 1933600ns - Issue to completion delay:
> 104800ns
> Buffer 90 - Read issue delay: 1943800ns - Issue to completion delay:
> 116100ns
> Buffer 91 - Read issue delay: 1962200ns - Issue to completion delay:
> 120500ns
> Buffer 92 - Read issue delay: 1980300ns - Issue to completion delay:
> 124200ns
> Buffer 93 - Read issue delay: 1990000ns - Issue to completion delay:
> 136500ns
> Buffer 94 - Read issue delay: 2008800ns - Issue to completion delay:
> 141600ns
> Buffer 95 - Read issue delay: 2028200ns - Issue to completion delay:
> 143100ns
> Buffer 96 - Read issue delay: 2044900ns - Issue to completion delay:
> 148900ns
> Buffer 97 - Read issue delay: 2054900ns - Issue to completion delay:
> 162300ns
> Buffer 98 - Read issue delay: 2072800ns - Issue to completion delay:
> 165600ns
> Buffer 99 - Read issue delay: 2094000ns - Issue to completion delay:
> 167500ns
> Buffer 100 - Read issue delay: 2103600ns - Issue to completion delay:
> 179000ns
> Buffer 101 - Read issue delay: 2126300ns - Issue to completion delay:
> 211400ns
> Buffer 102 - Read issue delay: 2145300ns - Issue to completion delay:
> 183400ns
> Buffer 103 - Read issue delay: 2163400ns - Issue to completion delay:
> 213400ns
> Buffer 104 - Read issue delay: 2183300ns - Issue to completion delay:
> 199300ns
> Buffer 105 - Read issue delay: 2192900ns - Issue to completion delay:
> 162900ns
> Buffer 106 - Read issue delay: 2215500ns - Issue to completion delay:
> 204700ns
> Buffer 107 - Read issue delay: 2233500ns - Issue to completion delay:
> 208700ns
> Buffer 108 - Read issue delay: 2252500ns - Issue to completion delay:
> 209000ns
> Buffer 109 - Read issue delay: 2271200ns - Issue to completion delay:
> 335600ns
> Buffer 110 - Read issue delay: 2281500ns - Issue to completion delay:
> 318400ns
> Buffer 111 - Read issue delay: 2301400ns - Issue to completion delay:
> 502400ns
> Buffer 112 - Read issue delay: 2320300ns - Issue to completion delay:
> 95200ns
> Buffer 113 - Read issue delay: 2339600ns - Issue to completion delay:
> 118700ns
>
> Disk E: (D: and E: are partitions on a 2Tb NVMe Seagate FireCuda
> ZP2000GM30013)
>
> PS E:\Test Data> FileReadSpeedTest '.\crystaldiskmark nvme ssd.png'
> Worker thread count: 6
> Clock is steady
> Buffer size: 512
> Open delay: 92800ns
> Open to read delay: 740200ns
> Buffer 0 - Read issue delay: 100ns - Issue to completion delay: 86554400ns
> Buffer 1 - Read issue delay: 73300ns - Issue to completion delay:
> 86443200ns
> Buffer 2 - Read issue delay: 89700ns - Issue to completion delay:
> 86286500ns
> Buffer 3 - Read issue delay: 101900ns - Issue to completion delay:
> 86296000ns
> Buffer 4 - Read issue delay: 131300ns - Issue to completion delay:
> 86413500ns
> Buffer 5 - Read issue delay: 145300ns - Issue to completion delay:
> 86577300ns
> Buffer 6 - Read issue delay: 160900ns - Issue to completion delay:
> 86331200ns
> Buffer 7 - Read issue delay: 177700ns - Issue to completion delay:
> 86872200ns
> Buffer 8 - Read issue delay: 190200ns - Issue to completion delay:
> 86602100ns
> Buffer 9 - Read issue delay: 208000ns - Issue to completion delay:
> 86819800ns
> Buffer 10 - Read issue delay: 224900ns - Issue to completion delay:
> 87068600ns
> Buffer 11 - Read issue delay: 237300ns - Issue to completion delay:
> 87051700ns
> Buffer 12 - Read issue delay: 255100ns - Issue to completion delay:
> 86892800ns
> Buffer 13 - Read issue delay: 269700ns - Issue to completion delay:
> 87075200ns
> Buffer 14 - Read issue delay: 280400ns - Issue to completion delay:
> 87179800ns
> Buffer 15 - Read issue delay: 293600ns - Issue to completion delay:
> 87354800ns
> Buffer 16 - Read issue delay: 306200ns - Issue to completion delay:
> 87297400ns
> Buffer 17 - Read issue delay: 317300ns - Issue to completion delay:
> 87524800ns
> Buffer 18 - Read issue delay: 329900ns - Issue to completion delay:
> 87433600ns
> Buffer 19 - Read issue delay: 343200ns - Issue to completion delay:
> 87455000ns
> Buffer 20 - Read issue delay: 355200ns - Issue to completion delay:
> 87613800ns
> Buffer 21 - Read issue delay: 368800ns - Issue to completion delay:
> 88039000ns
> Buffer 22 - Read issue delay: 380800ns - Issue to completion delay:
> 87908000ns
> Buffer 23 - Read issue delay: 391100ns - Issue to completion delay:
> 87971200ns
> Buffer 24 - Read issue delay: 403300ns - Issue to completion delay:
> 87870800ns
> Buffer 25 - Read issue delay: 416200ns - Issue to completion delay:
> 87816700ns
> Buffer 26 - Read issue delay: 427800ns - Issue to completion delay:
> 87685300ns
> Buffer 27 - Read issue delay: 443200ns - Issue to completion delay:
> 87811100ns
> Buffer 28 - Read issue delay: 456700ns - Issue to completion delay:
> 87682600ns
> Buffer 29 - Read issue delay: 467800ns - Issue to completion delay:
> 87583500ns
> Buffer 30 - Read issue delay: 480100ns - Issue to completion delay:
> 87518600ns
> Buffer 31 - Read issue delay: 493500ns - Issue to completion delay:
> 87727200ns
> Buffer 32 - Read issue delay: 503800ns - Issue to completion delay:
> 89320200ns
> Buffer 33 - Read issue delay: 518100ns - Issue to completion delay:
> 89303900ns
> Buffer 34 - Read issue delay: 533700ns - Issue to completion delay:
> 89251700ns
> Buffer 35 - Read issue delay: 549600ns - Issue to completion delay:
> 89216900ns
> Buffer 36 - Read issue delay: 566600ns - Issue to completion delay:
> 89181200ns
> Buffer 37 - Read issue delay: 579400ns - Issue to completion delay:
> 89148600ns
> Buffer 38 - Read issue delay: 590900ns - Issue to completion delay:
> 89204900ns
> Buffer 39 - Read issue delay: 604700ns - Issue to completion delay:
> 89104600ns
> Buffer 40 - Read issue delay: 616600ns - Issue to completion delay:
> 89069300ns
> Buffer 41 - Read issue delay: 627600ns - Issue to completion delay:
> 89065400ns
> Buffer 42 - Read issue delay: 779700ns - Issue to completion delay:
> 88885200ns
> Buffer 43 - Read issue delay: 793400ns - Issue to completion delay:
> 88855500ns
> Buffer 44 - Read issue delay: 804600ns - Issue to completion delay:
> 88833200ns
> Buffer 45 - Read issue delay: 817900ns - Issue to completion delay:
> 88821600ns
> Buffer 46 - Read issue delay: 831400ns - Issue to completion delay:
> 88780400ns
> Buffer 47 - Read issue delay: 842900ns - Issue to completion delay:
> 88775600ns
> Buffer 48 - Read issue delay: 854700ns - Issue to completion delay:
> 88733300ns
> Buffer 49 - Read issue delay: 866800ns - Issue to completion delay:
> 88715100ns
> Buffer 50 - Read issue delay: 878100ns - Issue to completion delay:
> 88684100ns
> Buffer 51 - Read issue delay: 891300ns - Issue to completion delay:
> 88642600ns
> Buffer 52 - Read issue delay: 903400ns - Issue to completion delay:
> 88554400ns
> Buffer 53 - Read issue delay: 915000ns - Issue to completion delay:
> 88520300ns
> Buffer 54 - Read issue delay: 927400ns - Issue to completion delay:
> 88488900ns
> Buffer 55 - Read issue delay: 1544000ns - Issue to completion delay:
> 87853500ns
> Buffer 56 - Read issue delay: 1556400ns - Issue to completion delay:
> 87822400ns
> Buffer 57 - Read issue delay: 1571200ns - Issue to completion delay:
> 87787800ns
> Buffer 58 - Read issue delay: 1583900ns - Issue to completion delay:
> 87755400ns
> Buffer 59 - Read issue delay: 1595800ns - Issue to completion delay:
> 87724500ns
> Buffer 60 - Read issue delay: 1608900ns - Issue to completion delay:
> 87692300ns
> Buffer 61 - Read issue delay: 1621800ns - Issue to completion delay:
> 87661000ns
> Buffer 62 - Read issue delay: 1633300ns - Issue to completion delay:
> 87862100ns
> Buffer 63 - Read issue delay: 1647100ns - Issue to completion delay:
> 87604000ns
> Buffer 64 - Read issue delay: 1659400ns - Issue to completion delay:
> 87585700ns
> Buffer 65 - Read issue delay: 1671600ns - Issue to completion delay:
> 87597300ns
> Buffer 66 - Read issue delay: 1684800ns - Issue to completion delay:
> 87535600ns
> Buffer 67 - Read issue delay: 1697100ns - Issue to completion delay:
> 87508500ns
> Buffer 68 - Read issue delay: 1709000ns - Issue to completion delay:
> 87474400ns
> Buffer 69 - Read issue delay: 1721500ns - Issue to completion delay:
> 87491700ns
> Buffer 70 - Read issue delay: 1733300ns - Issue to completion delay:
> 87426200ns
> Buffer 71 - Read issue delay: 1744800ns - Issue to completion delay:
> 87393300ns
> Buffer 72 - Read issue delay: 1756200ns - Issue to completion delay:
> 87347800ns
> Buffer 73 - Read issue delay: 1768100ns - Issue to completion delay:
> 87315800ns
> Buffer 74 - Read issue delay: 1779900ns - Issue to completion delay:
> 87285300ns
> Buffer 75 - Read issue delay: 1792400ns - Issue to completion delay:
> 87444300ns
> Buffer 76 - Read issue delay: 1804000ns - Issue to completion delay:
> 87267700ns
> Buffer 77 - Read issue delay: 1815100ns - Issue to completion delay:
> 87228600ns
> Buffer 78 - Read issue delay: 1826700ns - Issue to completion delay:
> 87190800ns
> Buffer 79 - Read issue delay: 1839800ns - Issue to completion delay:
> 87187400ns
> Buffer 80 - Read issue delay: 1851400ns - Issue to completion delay:
> 87135400ns
> Buffer 81 - Read issue delay: 1863700ns - Issue to completion delay:
> 87041800ns
> Buffer 82 - Read issue delay: 1876400ns - Issue to completion delay:
> 86996700ns
> Buffer 83 - Read issue delay: 1887600ns - Issue to completion delay:
> 86999400ns
> Buffer 84 - Read issue delay: 1899800ns - Issue to completion delay:
> 86946600ns
> Buffer 85 - Read issue delay: 1911600ns - Issue to completion delay:
> 86923800ns
> Buffer 86 - Read issue delay: 1922000ns - Issue to completion delay:
> 86816700ns
> Buffer 87 - Read issue delay: 1934200ns - Issue to completion delay:
> 86750400ns
> Buffer 88 - Read issue delay: 1946000ns - Issue to completion delay:
> 84927600ns
> Buffer 89 - Read issue delay: 1956500ns - Issue to completion delay:
> 84811300ns
> Buffer 90 - Read issue delay: 1968200ns - Issue to completion delay:
> 84941500ns
> Buffer 91 - Read issue delay: 1979500ns - Issue to completion delay:
> 85109100ns
> Buffer 92 - Read issue delay: 1990100ns - Issue to completion delay:
> 85260200ns
> Buffer 93 - Read issue delay: 2002400ns - Issue to completion delay:
> 85266500ns
> Buffer 94 - Read issue delay: 2015100ns - Issue to completion delay:
> 85142900ns
> Buffer 95 - Read issue delay: 2029500ns - Issue to completion delay:
> 85384900ns
> Buffer 96 - Read issue delay: 2042000ns - Issue to completion delay:
> 85487900ns
> Buffer 97 - Read issue delay: 2054300ns - Issue to completion delay:
> 85668700ns
> Buffer 98 - Read issue delay: 2255700ns - Issue to completion delay:
> 85606800ns
> Buffer 99 - Read issue delay: 2269400ns - Issue to completion delay:
> 85515700ns
> Buffer 100 - Read issue delay: 2281200ns - Issue to completion delay:
> 85704100ns
> Buffer 101 - Read issue delay: 2292000ns - Issue to completion delay:
> 85765900ns
> Buffer 102 - Read issue delay: 2306100ns - Issue to completion delay:
> 86201500ns
> Buffer 103 - Read issue delay: 2318800ns - Issue to completion delay:
> 86170400ns
> Buffer 104 - Read issue delay: 2329100ns - Issue to completion delay:
> 86079800ns
> Buffer 105 - Read issue delay: 2340600ns - Issue to completion delay:
> 85972700ns
> Buffer 106 - Read issue delay: 2353100ns - Issue to completion delay:
> 85594300ns
> Buffer 107 - Read issue delay: 2365000ns - Issue to completion delay:
> 86082600ns
> Buffer 108 - Read issue delay: 2377500ns - Issue to completion delay:
> 86156500ns
> Buffer 109 - Read issue delay: 2390200ns - Issue to completion delay:
> 86272000ns
> Buffer 110 - Read issue delay: 2400300ns - Issue to completion delay:
> 86392800ns
> Buffer 111 - Read issue delay: 2412200ns - Issue to completion delay:
> 86181900ns
> Buffer 112 - Read issue delay: 2423800ns - Issue to completion delay:
> 86238900ns
> Buffer 113 - Read issue delay: 2434200ns - Issue to completion delay:
> 86123900ns
> On 2025-09-25 03:44, Chris Blume (ProgramMax) wrote:
>
> Hello everyone,
>
> I just uploaded a first pass at a new tool to help us in our effort to
> improve PNG decoding,  FileReadSpeedTest
> <https://github.com/ProgramMax/FileReadSpeedTest>.
>
> It works by finding the optimal buffer size for a given drive & file
> system, then loads a file buffer-by-buffer. It reports the time each buffer
> arrives. This allows us to "replay" file loading for performance testing.
> (The drive and OS will cache data, changing the load speeds & performance
> results. We can instead feed the buffers to the test rig at known good
> intervals to keep tests consistent.)
>
> This is how the hardware works under the hood. It does not load an entire
> file in one go. This also gives us a target for our decode speeds. In an
> ideal world, we can decode a buffer faster than the next buffer arrives.
> That would mean the decode speed is limited by the drive, not the
> format/algorithm.
>
> I tested on my laptop, which has a WD_BLACK SN770 2TB drive. That is a
> seriously fast drive. Advertised speeds are "up to 5,150 MB/s". I was able
> to reach 5,259 MB/s. It is formatted with NTFS (BitLocker encrypted).
> Windows reports the ideal buffer size is 4096 bytes.
>
> A buffer load took ~10 microseconds. So a simple, not-quite-accurate
> reaction is "Our format should decode 4096 bytes in ~10 microseconds for
> this machine".
> For a machine with a more normal drive, we'll have even more time.
>
> (In order to be more accurate, I'll need to also measure IO command
> queuing and OS call overhead. That'll come soon.)
>
> An important thing to note is this is a moving target. CPU speeds have
> leveled out, but drive speeds are still increasing. If we want to target
> crazy fast server hardware, that's a different target. Additionally, that
> 4096 bytes in ~10 microseconds assumes a single-threaded workload. If we
> were able to spread the work across 8 threads, we would have ~80
> microseconds. But with command queuing, multiple threads worth of buffered
> data might arrive at nearly the same time, reducing the available
> per-thread decode time back down.
>
> I'll work on improving the tool and gathering more sample data for us to
> replay under various conditions. I'll also add Linux and Mac support when I
> can.
>
> --
> Chris Lilley
> @svgeesus@mastodon.scot
> W3C Distinguished Expert, Color, Graphics & Fonts
> W3C Technical Programming Team, Core Web Design
>
>