From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 6D4C36B00AD for ; Thu, 11 Nov 2010 21:44:13 -0500 (EST) Date: Thu, 11 Nov 2010 18:40:59 -0800 From: Andrew Morton Subject: Re: [PATCH][RESEND] nommu: yield CPU periodically while disposing large VM Message-Id: <20101111184059.5744a42f.akpm@linux-foundation.org> In-Reply-To: <1289507596-17613-1-git-send-email-steve@digidescorp.com> References: <1289507596-17613-1-git-send-email-steve@digidescorp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: "Steven J. Magnani" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Greg Ungerer List-ID: On Thu, 11 Nov 2010 14:33:16 -0600 "Steven J. Magnani" wrote: > Depending on processor speed, page size, and the amount of memory a process > is allowed to amass, cleanup of a large VM may freeze the system for many > seconds. This can result in a watchdog timeout. hm, that's no good. > Make sure other tasks receive some service when cleaning up large VMs. > > Signed-off-by: Steven J. Magnani > --- > diff -uprN a/mm/nommu.c b/mm/nommu.c > --- a/mm/nommu.c 2010-10-21 07:42:23.000000000 -0500 > +++ b/mm/nommu.c 2010-10-21 07:46:50.000000000 -0500 > @@ -1656,6 +1656,7 @@ SYSCALL_DEFINE2(munmap, unsigned long, a > void exit_mmap(struct mm_struct *mm) > { > struct vm_area_struct *vma; > + unsigned long next_yield = jiffies + HZ; > > if (!mm) > return; > @@ -1668,6 +1669,11 @@ void exit_mmap(struct mm_struct *mm) > mm->mmap = vma->vm_next; > delete_vma_from_mm(vma); > delete_vma(mm, vma); > + /* Yield periodically to prevent watchdog timeout */ > + if (time_after(jiffies, next_yield)) { > + cond_resched(); > + next_yield = jiffies + HZ; > + } > } > > kleave(""); You might be able to do this a bit more neatly with __ratelimit: DEFINE_RATELIMIT_STATE(rl, HZ, 1); ... if (___ratelimit(&rl, NULL)) cond_resched(); but ___ratelimit() isn't really ready for that - it still has (easily fixed) assumptions that it's being used for printk ratelimiting. But anyway. cond_resched() is pretty efficient and one second is still a very long time. I suspect you don't need the ratelimiting at all? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org