Date: Sun, 19 Nov 2017 10:40:24 -0500 From: Pedro Giffuni <pfg@FreeBSD.org> To: trasz@FreeBSD.org, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r325965 - head/libexec/rtld-elf Message-ID: <dc068781-d210-f874-ef62-02d9fa8a04d0@FreeBSD.org> In-Reply-To: <20171119121245.GA88868@brick> References: <201711181321.vAIDLM6S028725@repo.freebsd.org> <20171118141007.GI2272@kib.kiev.ua> <20171119121245.GA88868@brick>
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On 11/19/17 07:12, Edward Tomasz Napierala wrote: > On 1118T1610, Konstantin Belousov wrote: >> On Sat, Nov 18, 2017 at 01:21:22PM +0000, Edward Tomasz Napierala wrote: >>> Author: trasz >>> Date: Sat Nov 18 13:21:22 2017 >>> New Revision: 325965 >>> URL: https://svnweb.freebsd.org/changeset/base/325965 >>> >>> Log: >>> Increase rtld initial memory pool size from 32kB to 128kB. >>> >>> The old value was probably fine back in 1998, when that code was imported >>> (although the comments still mention VAX, which was quite obsolete by then); >>> now, however, it's too small to handle our libc, which results in some >>> additional calls to munmap/mmap later on. Asking for more virtual address >>> space is virtually free, and syscalls are not, thus the change. >>> >>> It was suggested by kib@ that this might be a symptom of a deeper problem. >>> It doesn't only affect libc, though - the change also improves rtld memory >>> management for eg KDE libraries. I guess it's just a natural bloat. >> This is not what I said. >> >> My guess was that the large allocation you see in the ktrace output as >> coming from rtld was really an allocation of the TLS segment, and it was >> so large because libc has that large TLS segment. You did not checked this >> guess against the actual code. > Right, I stand corrected. > >> If my guess is true, I do not see a point in the change you made: the >> memory consumption is externally imposed on rtld, and we should not try >> to tailor it to single, whenever important, consumer. > Here's where I disagree. The rtld is not some abstract concept, it's one > of the components of the operating system, and it can and should be tweaked > to match real life situations. Especially when it affects virtually all > of its use cases, as is the case with libc. > > Being pragmatic ... Determining such values is almost always a trial-and-error process. Perhaps 64k is makes everyone (especially KDE) happy? Pedro.
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