Re: BUFSIZ-related pessimization in fvwrite.c

[christos%astron.com@localhost (Christos Zoulas)]

In article <CAJgzZoqnbmNtYQm9TswYc36deWm802YMbyHBuw+5hF1=4=Ue5g%mail.gmail.com@localhost>,
enh  <enh%google.com@localhost> wrote:
>(if anyone knows the equivalent freebsd list, please add them --- this
>code is the same between all three bsds.)
>
>Apple patched their copy of the FreeBSD fvwrite.c to change BUFSIZ to
>INT_MAX to massively improve the performance of large unbuffered
>writes[1], and patched the buffered case to use the largest multiple
>of the buffer size to massively improve the performance of large
>buffered writes:
>
>https://github.com/apple-oss-distributions/Libc/commit/c5a3293354e22262702a3add5b2dfc9bb0b93b85#diff-3b844a19cfb0aab1a23f7fbc457d3bce7453513730c489a72f66ff89d6557ff3
>
>i've tested similar changes to openbsd's fvwrite.c with great results.
>
>is it a _requirement_ that buffered writes _only_ happen in multiples
>of the buffer size? that seems unlikely to me (a) because of short
>writes and (b) musl just does a writev() of what's in the buffer and
>what it was just given in case of a larger-than-buffer write and (c)
>we already changed the openbsd fread() to read directly into the
>caller's buffer regardless of size, so the equivalent behavior on the
>_write_ side seems reasonable to me?

Makes sense, committed.

christos