Date: Tue, 29 Dec 2015 11:37:42 -0800 From: John Baldwin <jhb@freebsd.org> To: Warner Losh <imp@bsdimp.com> Cc: src-committers <src-committers@freebsd.org>, svn-src-head@freebsd.org, svn-src-all@freebsd.org, Warner Losh <imp@freebsd.org> Subject: Re: svn commit: r292809 - head/lib/libc/stdio Message-ID: <2345870.SHMMVrpc1D@ralph.baldwin.cx> In-Reply-To: <CANCZdfq4sMAEzJ-wxNnybJiiTnJV3k5NZgcQACnchHCgpKQxrQ@mail.gmail.com> References: <201512272304.tBRN4C5D034464@repo.freebsd.org> <41508412.yspAtSoPCD@ralph.baldwin.cx> <CANCZdfq4sMAEzJ-wxNnybJiiTnJV3k5NZgcQACnchHCgpKQxrQ@mail.gmail.com>
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On Monday, December 28, 2015 01:01:26 PM Warner Losh wrote: > I'll look at that, but I don't think posix_memalign is the right way to go. > The alignment of FILE is more strict than posix_memalign will return. Ian's > idea of __alignof__ is the way to go. We allocate them in one block on > purpose for performance, and posix_memalign would be a one at a time affair. posix_memalign gives you whatever alignment you ask for. Using __alignof__ to determine the alignment instead of hardcoding sizeof(int64_t) would certainly be an improvement. If you move the glue after the FILE objects then you can use posix_memalign() directly as so: void *mem; int error; error = posix_memalign(&mem, MAX(ALIGNBYTES, __alignof__(mbstate_t)), n * sizeof(FILE) + sizeof(*g)); if (error) return (NULL); p = (FILE *)mem; g = (struct glue *)(p + n); g->next = NULL; g->niobs = n; g->iobs = p; ... (This presumes that the requested alignment of 'struct glue' is less than the alignment needed by FILE which should be true.) -- John Baldwin
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