From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
To: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: kexec mailing list <kexec@lists.infradead.org>,
Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>,
Petr Tesarik <ptesarik@suse.cz>, Jan Willeke <willeke@de.ibm.com>
Subject: Re: [PATCH v2 0/8] Handle mmaped regions in cache [more analysis]
Date: Thu, 12 Mar 2015 14:56:16 +0100 [thread overview]
Message-ID: <20150312145616.721b1e37@holzheu> (raw)
In-Reply-To: <20150309170858.0e8bf357@holzheu>
On Mon, 9 Mar 2015 17:08:58 +0100
Michael Holzheu <holzheu@linux.vnet.ibm.com> wrote:
> Hello Petr,
>
[snip]
> As a conclusion, we could think of mapping larger chunks
> also for the fragmented case of -d 31 to reduce the amount
> of mmap/munmap calls.
>
FYI: I did some more tests and I am no longer sure if the above
conclusion was correct.
A simple "copy" program that reads or maps/unmaps every page
from /proc/vmcore and then writes it to /dev/null is faster
with mmap()/munmap() than with using read():
read:
-----
# time ./copy /dev/null read
real 0m1.072s
user 0m0.010s
sys 0m1.054s
# perf stat -e syscalls:sys_enter_old_mmap,syscalls:sys_enter_munmap,syscalls:sys_enter_read ./copy /dev/null read
8 syscalls:sys_enter_old_mmap
1 syscalls:sys_enter_munmap
458753 syscalls:sys_enter_read
1.405457536 seconds time elapsed
mmap:
-----
# time ./copy /dev/null mmap
real 0m0.947s
user 0m0.314s
sys 0m0.631s
# perf stat -e syscalls:sys_enter_old_mmap,syscalls:sys_enter_munmap,syscalls:sys_enter_read ./copy /dev/null mmap
458760 syscalls:sys_enter_old_mmap
458753 syscalls:sys_enter_munmap
1 syscalls:sys_enter_read
1.175956735 seconds time elapsed
Regards,
Michael
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next prev parent reply other threads:[~2015-03-12 13:56 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-06 14:03 [PATCH v2 0/8] Handle mmaped regions in cache Petr Tesarik
2015-03-06 8:23 ` [PATCH v2 1/8] cache: get rid of search loop in cache_add() Petr Tesarik
2015-03-06 8:52 ` [PATCH v2 2/8] cache: allow to return a page to the pool Petr Tesarik
2015-03-06 8:59 ` [PATCH v2 3/8] cache: do not allocate from the pending list Petr Tesarik
2015-03-06 9:26 ` [PATCH v2 4/8] cache: add hit/miss statistics to the final report Petr Tesarik
2015-03-06 13:07 ` [PATCH v2 5/8] cache: allocate buffers in one big chunk Petr Tesarik
2015-03-06 13:10 ` [PATCH v2 6/8] cache: allow arbitrary size of cache entries Petr Tesarik
2015-03-06 13:23 ` [PATCH v2 7/8] cache: store mapped regions directly in the cache Petr Tesarik
2015-03-06 13:28 ` [PATCH v2 8/8] cleanup: remove unused page_is_fractional Petr Tesarik
2015-03-09 16:08 ` [PATCH v2 0/8] Handle mmaped regions in cache Michael Holzheu
2015-03-09 16:08 ` [PATCH v2 0/8] Handle mmaped regions in cache [more analysis] Michael Holzheu
2015-03-12 13:56 ` Michael Holzheu [this message]
2015-03-12 15:38 ` Petr Tesarik
2015-03-13 4:10 ` Atsushi Kumagai
2015-03-13 8:04 ` Petr Tesarik
2015-03-16 5:14 ` Atsushi Kumagai
2015-03-16 7:26 ` Petr Tesarik
2015-03-16 8:06 ` Atsushi Kumagai
2015-03-16 8:24 ` Petr Tesarik
2015-03-13 16:19 ` Michael Holzheu
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