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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