On Fri, 25 Oct 2013, NeilBrown wrote:
On Fri, 25 Oct 2013 07:25:13 +0000 (UTC) "Artem S. Tashkinov"
<t.artem@xxxxxxxxx> wrote:
Hello!
On my x86-64 PC (Intel Core i5 2500, 16GB RAM), I have the same 3.11 kernel
built for the i686 (with PAE) and x86-64 architectures. What's really troubling me
is that the x86-64 kernel has the following problem:
When I copy large files to any storage device, be it my HDD with ext4 partitions
or flash drive with FAT32 partitions, the kernel first caches them in memory entirely
then flushes them some time later (quite unpredictably though) or immediately upon
invoking "sync".
How can I disable this memory cache altogether (or at least minimize caching)? When
running the i686 kernel with the same configuration I don't observe this effect - files get
written out almost immediately (for instance "sync" takes less than a second, whereas
on x86-64 it can take a dozen of _minutes_ depending on a file size and storage
performance).
What exactly is bothering you about this? The amount of memory used or the
time until data is flushed?
actually, I think the problem is more the impact of the huge write later on.
David Lang
If the later, then /proc/sys/vm/dirty_expire_centisecs is where you want to
look.
This defaults to 30 seconds (3000 centisecs).
You could make it smaller (providing you also shrink
dirty_writeback_centisecs in a similar ratio) and the VM will flush out data
more quickly.
NeilBrown
I'm _not_ talking about disabling write cache on my storage itself (hdparm -W 0 /dev/XXX)
- firstly this command is detrimental to the performance of my PC, secondly, it won't help
in this instance.
Swap is totally disabled, usually my memory is entirely free.
My kernel configuration can be fetched here: https://bugzilla.kernel.org/show_bug.cgi?id=63531
Please, advise.
Best regards,
Artem
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