Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753370AbYJ3Et7 (ORCPT ); Thu, 30 Oct 2008 00:49:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751738AbYJ3Ett (ORCPT ); Thu, 30 Oct 2008 00:49:49 -0400 Received: from cantor2.suse.de ([195.135.220.15]:49166 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751615AbYJ3Ets (ORCPT ); Thu, 30 Oct 2008 00:49:48 -0400 Date: Thu, 30 Oct 2008 05:49:41 +0100 From: Nick Piggin To: Glauber Costa Cc: Avi Kivity , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, aliguori@codemonkey.ws, Jeremy Fitzhardinge , Krzysztof Helt Subject: Re: [PATCH] regression: vmalloc easily fail. Message-ID: <20081030044941.GA9470@wotan.suse.de> References: <1225234513-3996-1-git-send-email-glommer@redhat.com> <20081028232944.GA3759@wotan.suse.de> <20081029094856.GD4269@poweredge.glommer> <20081029101145.GB5953@wotan.suse.de> <49083B14.6070402@redhat.com> <20081029104333.GD5953@wotan.suse.de> <20081029220737.GF11532@poweredge.glommer> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081029220737.GF11532@poweredge.glommer> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4103 Lines: 128 On Wed, Oct 29, 2008 at 08:07:37PM -0200, Glauber Costa wrote: > On Wed, Oct 29, 2008 at 11:43:33AM +0100, Nick Piggin wrote: > > On Wed, Oct 29, 2008 at 12:29:40PM +0200, Avi Kivity wrote: > > > Nick Piggin wrote: > > > >Hmm, spanning <30MB of memory... how much vmalloc space do you have? > > > > > > > > > > > > > > From the original report: > > > > > > >VmallocTotal: 122880 kB > > > >VmallocUsed: 15184 kB > > > >VmallocChunk: 83764 kB > > > > > > So it seems there's quite a bit of free space. > > > > > > Chunk is the largest free contiguous region, right? If so, it seems the > > > > Yes. > > > > > > > problem is unrelated to guard pages, instead the search isn't finding a > > > 1-page area (with two guard pages) for some reason, even though lots of > > > free space is available. > > > > Hmm. The free area search could be buggy... > Do you want me to grab any specific info of it? Or should I just hack myself > randomly into it? I'll probably have some time for that tomorrow. I took a bit of a look. Does this help you at all? I still think we should get rid of the guard pages in non-debug kernels completely, but hopefully this will fix your problems? -- - Fix off by one bug in the KVA allocator that can leave gaps - An initial vmalloc failure should start off a synchronous flush of lazy areas, in case someone is in progress flushing them already. - Purge lock can be a mutex so we can sleep while that's going on. Signed-off-by: Nick Piggin --- Index: linux-2.6/mm/vmalloc.c =================================================================== --- linux-2.6.orig/mm/vmalloc.c +++ linux-2.6/mm/vmalloc.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include #include @@ -362,7 +363,7 @@ retry: goto found; } - while (addr + size >= first->va_start && addr + size <= vend) { + while (addr + size > first->va_start && addr + size <= vend) { addr = ALIGN(first->va_end + PAGE_SIZE, align); n = rb_next(&first->rb_node); @@ -472,7 +473,7 @@ static atomic_t vmap_lazy_nr = ATOMIC_IN static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end, int sync, int force_flush) { - static DEFINE_SPINLOCK(purge_lock); + static DEFINE_MUTEX(purge_lock); LIST_HEAD(valist); struct vmap_area *va; int nr = 0; @@ -483,10 +484,10 @@ static void __purge_vmap_area_lazy(unsig * the case that isn't actually used at the moment anyway. */ if (!sync && !force_flush) { - if (!spin_trylock(&purge_lock)) + if (!mutex_trylock(&purge_lock)) return; } else - spin_lock(&purge_lock); + mutex_lock(&purge_lock); rcu_read_lock(); list_for_each_entry_rcu(va, &vmap_area_list, list) { @@ -518,7 +519,18 @@ static void __purge_vmap_area_lazy(unsig __free_vmap_area(va); spin_unlock(&vmap_area_lock); } - spin_unlock(&purge_lock); + mutex_unlock(&purge_lock); +} + +/* + * Kick off a purge of the outstanding lazy areas. Don't bother if somebody + * is already purging. + */ +static void try_purge_vmap_area_lazy(void) +{ + unsigned long start = ULONG_MAX, end = 0; + + __purge_vmap_area_lazy(&start, &end, 0, 0); } /* @@ -528,7 +540,7 @@ static void purge_vmap_area_lazy(void) { unsigned long start = ULONG_MAX, end = 0; - __purge_vmap_area_lazy(&start, &end, 0, 0); + __purge_vmap_area_lazy(&start, &end, 1, 0); } /* @@ -539,7 +551,7 @@ static void free_unmap_vmap_area(struct va->flags |= VM_LAZY_FREE; atomic_add((va->va_end - va->va_start) >> PAGE_SHIFT, &vmap_lazy_nr); if (unlikely(atomic_read(&vmap_lazy_nr) > lazy_max_pages())) - purge_vmap_area_lazy(); + try_purge_vmap_area_lazy(); } static struct vmap_area *find_vmap_area(unsigned long addr) -- 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/