Messages in this thread | | | Date | Mon, 20 Dec 2004 13:43:34 -0200 | From | Marcelo Tosatti <> | Subject | Re: Reducing inode cache usage on 2.4? |
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On Mon, Dec 20, 2004 at 06:54:09PM +0100, Andrea Arcangeli wrote: > On Mon, Dec 20, 2004 at 01:06:34PM -0200, Marcelo Tosatti wrote: > > The thing is right now we dont try to reclaim from icache/dcache _at all_ > > if enough clean pagecache pages are found and reclaimed. > > > > Its sounds unfair to me. > > If most ram is in pagecache there's not much point to shrink the dcache. > The more ram goes into dcache/icache, the less ram will be in pagecache, > and the more likely we'll start shrinking dcache/icache. Also keep in > mind in a highmem machine the pagecache will be in highmemory and the > dcache/icache in lowmemory (on very very big boxes the lowmem_reserve > algorithm pratically splits the two in non-overkapping zones), so > especially on a big highmem machine shrinking dcache/icache during a > pagecache allocation (because this is what the workload is doing: only > pagecache allocations) is a worthless effort. > > This is the best solution we have right now, but there have been several > discussions in the past on how to shrink dcache/icache. But if we want > to talk on how to change this, we should talk about 2.6/2.7 only IMHO. > > > Why not? If we have a lot of them they will probably be hurting performace, which seems > > to be the case now. > > The slowdown could be because the icache/dcache hash size is too small. > It signals collisions in the dcache/icache hashtable. 2.6 with bootmem > allocated hashes should be better. Optimizing 2.4 for performance if not > worth the risk IMHO. I would suggest to check if you can reproduce in > 2.6, and fix it there, if it's still there. > > > Following this logic any workload which generates pagecache and happen > > to, most times, have enough pagecache clean to be reclaimed should not > > reclaim the i/dcache's. Which is not right. > > This mostly happens for cache-polluting-workloads like in this testcase. > If the cache would be activated, there would be less pages in the > inactive list and you had a better chance to invoke the dcache/icache > shrinking.
OK I buy your arguments I'll revert Andrew's patch. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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