Re: What is the limit size of tmpfs /dev/shm ?

From: H. Peter Anvin
Date: Wed Feb 06 2008 - 17:02:24 EST


Hugh Dickins wrote:
On Wed, 6 Feb 2008, H. Peter Anvin wrote:
That sounds like a problem in our overall swap handling, not specifically in
tmpfs. Now, I can't say anything concrete about heavy swap conditions, but in
light swap conditions I have measured a 20x performance improvement(!) over
ext3 on real workloads.

Wow, I'm surprised. I suppose I do jump to thinking of heavy swapping
when light swapping won't be so bad; but even so, 20x ext3 astonishes
me - ext3 wouldn't be anyone's choice for fastest, but even so...

I certainly guess too much and measure too little:
is there a useful test you could point me to? TIA


The specific application was this:

- extract a kernel tarball
- "make distclean"
- cp -al the resulting tree
- apply a patch to each tree
- do a diff between the trees
- delete all files

... repeat something like 20,000 times.

-hpa
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