Re: VFS: file-max limit 50044 reached

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Dipankar Sarma a écrit :
On Mon, Oct 17, 2005 at 09:16:25AM -0700, Linus Torvalds wrote:

Absolutely. Keeping a count of (percpu) queued items is basically free if kept
in the cache line used by list head, so the 'queue length on this cpu' is a
cheap metric.

The only downside to TIF_RCUUPDATE is that those damn TIF-flags are per-architecture (probably largely unnecessary, but while most architectures don't care at all, others seem to have optimized their layout so that they can test the work bits more efficiently). So it's a matter of each architecture being updated with its TIF_xyz flag and their work function.

Anybody willing to try? Dipankar apparently has a lot on his plate, this _should_ be fairly straightforward. Eric?


I *had*, when this hit me :) It was one those spurt things. I am going to
look at this, but I think we will need to do this with some careful
benchmarking.

At the moment however I do have another concern - open/close taking too
much time as I mentioned in an earlier email. It is nearly 4 times
slower than 2.6.13. So, that is first up in my list of things to
do at the moment.


<lazy_mode=ON>
Do we really need a TIF_RCUUPDATE flag, or could we just ask for a resched ?
</lazy_mode>

This patch only take care of call_rcu(), I'm unsure of what can be done inside call_rcu_bh()

The two stress program dont hit OOM anymore with this patch applied (even with maxbatch=10)

Eric

--- linux-2.6.14-rc4/kernel/rcupdate.c	2005-10-11 03:19:19.000000000 +0200
+++ linux-2.6.14-rc4-ed/kernel/rcupdate.c	2005-10-17 21:52:18.000000000 +0200
@@ -109,6 +109,10 @@
 	rdp = &__get_cpu_var(rcu_data);
 	*rdp->nxttail = head;
 	rdp->nxttail = &head->next;
+
+	if (unlikely(++rdp->count > 10000))
+		set_need_resched();
+
 	local_irq_restore(flags);
 }
 
@@ -140,6 +144,12 @@
 	rdp = &__get_cpu_var(rcu_bh_data);
 	*rdp->nxttail = head;
 	rdp->nxttail = &head->next;
+	rdp->count++;
+/*
+ *  Should we directly call rcu_do_batch() here ?
+ *  if (unlikely(rdp->count > 10000))
+ *      rcu_do_batch(rdp);
+ */
 	local_irq_restore(flags);
 }
 
@@ -157,6 +167,7 @@
 		next = rdp->donelist = list->next;
 		list->func(list);
 		list = next;
+		rdp->count--;
 		if (++count >= maxbatch)
 			break;
 	}
--- linux-2.6.14-rc4/include/linux/rcupdate.h	2005-10-11 03:19:19.000000000 +0200
+++ linux-2.6.14-rc4-ed/include/linux/rcupdate.h	2005-10-17 21:02:25.000000000 +0200
@@ -94,6 +94,7 @@
 	long  	       	batch;           /* Batch # for current RCU batch */
 	struct rcu_head *nxtlist;
 	struct rcu_head **nxttail;
+	long            count; /* # of queued items */
 	struct rcu_head *curlist;
 	struct rcu_head **curtail;
 	struct rcu_head *donelist;

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