Hacker News: gaul

The more general-purpose -Wconversion has many false positives, often around int to char conversion. Some functions like int toupper(int) have an unexpected int return type to deal with special out-of-bound values like EOF.

New comment by gaul in "Branch predictor: How many “if”s are too many?"

gaul — Sat, 08 May 2021 01:17:02 +0000

This is not a NOP; it explicitly clears the upper 32 bits of EDI since the compiler does not know that they are zero in this situation. If you change cc from an int to size_t (long on x86-64) the compiler will generate:

        mov     eax, OFFSET FLAT:.LC0
        cmp     rdi, 258
        ja      .L1
        mov     rax, QWORD PTR CSWTCH.1[0+rdi*8]

Note that in some cases the compiler can do this automatically via lifetime analysis but not in this freestanding example.

New comment by gaul in "Dropping Hashes (2020)"

gaul — Mon, 29 Mar 2021 15:19:24 +0000

Robert O'Callahan hashed some thoughts about Firefox that he revealed many years later:

https://robert.ocallahan.org/2018/01/ancient-browser-wars-hi...

New comment by gaul in "The Evolution of the QEMU Translator"

gaul — Sat, 30 Jan 2021 13:15:09 +0000

HP Dynamo is similar to what you suggest:

https://www.hpl.hp.com/techreports/1999/HPL-1999-78.html

Note that CPUs and compiler optimization have improved over the last 20 years and these results may not still hold.

New comment by gaul in "The future of 32-bit Linux"

gaul — Sat, 05 Dec 2020 13:31:44 +0000

The article mentions 32-bit Raspbian which is moving to 64-bit to better support the Raspberry Pi 4 with 8 GB of RAM. Both the RPi 3 and 4 have 64-bit support but earlier models, including the popular and still-on-sale Zero, do not support 64-bit. This platform will likely stick around for a long time; we need to continue to fix issues like this size_t/off_t one in s3fs:

https://github.com/s3fs-fuse/s3fs-fuse/pull/1039

New comment by gaul in "S3 Strong Consistency"

gaul — Wed, 02 Dec 2020 04:47:21 +0000

Thanks for testing! You may improve performance via increasing -o parallel_count (default="5"). Newer versions of s3fs have improved performance but please report any cliffs at https://github.com/s3fs-fuse/s3fs-fuse/issues .

New comment by gaul in "S3 Strong Consistency"

gaul — Wed, 02 Dec 2020 02:21:12 +0000

This is great news for application developers! And probably hard work for the AWS implementors. I will try to update this over the weekend: https://github.com/gaul/are-we-consistent-yet

New comment by gaul in "S3 Strong Consistency"

gaul — Wed, 02 Dec 2020 02:01:37 +0000

Could you expand on this comment? s3fs uses multiple threads for uploading and populating readdir metadata via S3fsMultiCurl::MultiPerform. Earlier versions used curl_multi_perform which may have hidden some of the parallelism from you.