Mapped more than Cached in /proc/meminfo
Hi, I am trying to analyze memory usage on my system. As first step I am monitoring /proc/meminfo. Surprisingly I see Mapped value is more than Cached. So in which case is it possible to have Mapped more than Cached ? Regards, ~/
On Fri, Aug 5, 2011 at 21:16, =/_00/\/\ <z0032oom@gmail.com> wrote:
Hi,
I am trying to analyze memory usage on my system. As first step I am monitoring /proc/meminfo. Surprisingly I see Mapped value is more than Cached.
So in which case is it possible to have Mapped more than Cached ?
your apps mmap() less than the amount of files content that are cached through normal read() AFAIK -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com
Hi, Thanks for replying Here is one observation worth mentioning. On boot system it shows Mapped < Cached (In fact much less) After using system for some time following commands are executed. # sync and echo 3 > /proc/sys/vm/drop_cache Whenever above command is executed I can see Mapped > Cached. This is somewhat confusing for me. Could you please explain ? Regards, ~/ On Sat, Aug 6, 2011 at 9:57 AM, Mulyadi Santosa <mulyadi.santosa@gmail.com>wrote:
On Fri, Aug 5, 2011 at 21:16, =/_00/\/\ <z0032oom@gmail.com> wrote:
Hi,
I am trying to analyze memory usage on my system. As first step I am monitoring /proc/meminfo. Surprisingly I see Mapped value is more than Cached.
So in which case is it possible to have Mapped more than Cached ?
your apps mmap() less than the amount of files content that are cached through normal read() AFAIK
-- regards,
Mulyadi Santosa Freelance Linux trainer and consultant
blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com
On Tue, Aug 9, 2011 at 3:10 PM, =/_00/\/\ <z0032oom@gmail.com> wrote:
Hi,
Thanks for replying Here is one observation worth mentioning. On boot system it shows Mapped < Cached (In fact much less) After using system for some time following commands are executed. # sync and echo 3 > /proc/sys/vm/drop_cache
Whenever above command is executed I can see Mapped > Cached.
This is somewhat confusing for me. Could you please explain ?
Regards, ~/
On Sat, Aug 6, 2011 at 9:57 AM, Mulyadi Santosa <mulyadi.santosa@gmail.com> wrote:
On Fri, Aug 5, 2011 at 21:16, =/_00/\/\ <z0032oom@gmail.com> wrote:
Hi,
I am trying to analyze memory usage on my system. As first step I am monitoring /proc/meminfo. Surprisingly I see Mapped value is more than Cached.
So in which case is it possible to have Mapped more than Cached ?
your apps mmap() less than the amount of files content that are cached through normal read() AFAIK
-- regards,
Mulyadi Santosa Freelance Linux trainer and consultant
blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com
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Please, read some explanation about this command, for instance, in [1] [1] http://linux-mm.org/Drop_Caches
Hi/// On 09/08/2011, =/_00/\/\ <z0032oom@gmail.com> wrote:
Hi,
Thanks for replying Here is one observation worth mentioning. On boot system it shows Mapped < Cached (In fact much less)
quite predictable.... during booting phase, your system read() much by doesn't mmap() that much....
After using system for some time following commands are executed. # sync and echo 3 > /proc/sys/vm/drop_cache
Whenever above command is executed I can see Mapped > Cached.
by echoing "3" to drop_cache, you flush the content of page cache as much as possible ... -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com
On Wed, Aug 10, 2011 at 12:56 PM, Mulyadi Santosa <mulyadi.santosa@gmail.com
wrote:
Hi///
On 09/08/2011, =/_00/\/\ <z0032oom@gmail.com> wrote:
Hi,
Thanks for replying Here is one observation worth mentioning. On boot system it shows Mapped < Cached (In fact much less)
quite predictable.... during booting phase, your system read() much by doesn't mmap() that much....
After using system for some time following commands are executed. # sync and echo 3 > /proc/sys/vm/drop_cache
Whenever above command is executed I can see Mapped > Cached.
by echoing "3" to drop_cache, you flush the content of page cache as much as possible ...
Here is my understanding of what drop_page_cache does: All page-cache pages are 'dropped' except the following: 1. Dirty pages. (they are *not* synced) 2. Mapped pages (pages 'in use' , mapped by rmap ) (There are a few more exceptions i dont recall now.) Hence even after dropping caches, free will still show some cached pages. These are dirty+mapped. Doing a sync before dropping will only show the mapped pages.
Hi, Please find my reply inlined. On Wed, Aug 10, 2011 at 1:04 PM, Prateek Sharma <prateek3.14@gmail.com>wrote:
On Wed, Aug 10, 2011 at 12:56 PM, Mulyadi Santosa < mulyadi.santosa@gmail.com> wrote:
Hi///
On 09/08/2011, =/_00/\/\ <z0032oom@gmail.com> wrote:
Hi,
Thanks for replying Here is one observation worth mentioning. On boot system it shows Mapped < Cached (In fact much less)
quite predictable.... during booting phase, your system read() much by doesn't mmap() that much....
After using system for some time following commands are executed. # sync and echo 3 > /proc/sys/vm/drop_cache
Whenever above command is executed I can see Mapped > Cached.
by echoing "3" to drop_cache, you flush the content of page cache as much as possible ...
Here is my understanding of what drop_page_cache does: All page-cache pages are 'dropped' except the following: 1. Dirty pages. (they are *not* synced) 2. Mapped pages (pages 'in use' , mapped by rmap ) (There are a few more exceptions i dont recall now.)
But even in this case Cached (/proc/meminfo) should be always greater than Mapped(/proc/meminfo) (As it will contain mapped + Unmapped pages) I also saw that Cached (/proc/meminfo) does not include Buffer Cache. ========= fs/proc/meminfo.c ======== cached = global_page_state(NR_FILE_PAGES) - total_swapcache_pages - i.bufferram; ============================== Even if drop_cache is not done is it ever possible to get Cached < Mapped ? Regards, ~/
participants (4)
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=/_00/\/\ -
Mulyadi Santosa -
Prateek Sharma -
Vladimir Murzin