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Subject: Re: jemalloc enhancement for small-memory systems
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From: Tim Kientzle <tim@kientzle.com>
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On Dec 22, 2012, at 11:28 AM, Ian Lepore wrote:

> When a daemon such as watchdogd uses mlockall(2) on a small-memory
> embedded system, it can end up wiring much of the available ram =
because
> jemalloc allocates large chunks of vmspace by default.  More =
background
> info on this can be found in this thread:
>=20
> =
http://lists.freebsd.org/pipermail/freebsd-embedded/2012-November/001679.h=
tml
>=20
> It's hard to tune jemalloc's allocation behavior for this in a
> machine-independent way because the minimum chunk size depends on
> PAGE_SIZE and other factors internal to jemalloc.  I've created a =
patch
> that addresses this by defining that lg_chunk:0 is implicitly a =
request
> to set the chunk size to the smallest value allowable for the machine
> it's running on.  The patch is attached to this PR...
>=20
> http://www.freebsd.org/cgi/query-pr.cgi?pr=3D174641
>=20
> Jason, could you please review this and consider incorporating it into
> jemalloc?  Or let us know if there's a better way to handle this
> situation.

Would it be feasible for jemalloc to initially allocate
small blocks (to not over-allocate for small programs and
systems with small RAM) and then allocate successively
larger blocks as the program requires more memory?

Tim