Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752808AbcL2Jnr (ORCPT ); Thu, 29 Dec 2016 04:43:47 -0500 Received: from mx2.suse.de ([195.135.220.15]:55076 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752731AbcL2Jnp (ORCPT ); Thu, 29 Dec 2016 04:43:45 -0500 Date: Thu, 29 Dec 2016 10:43:36 +0100 From: Michal Hocko To: Jaewon Kim Cc: gregkh@linuxfoundation.org, akpm@linux-foundation.org, labbott@redhat.com, mina86@mina86.com, m.szyprowski@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com Subject: Re: [PATCH] mm: cma: print allocation failure reason and bitmap status Message-ID: <20161229094335.GH29208@dhcp22.suse.cz> References: <1482978482-14007-1-git-send-email-jaewon31.kim@samsung.com> <20161229091449.GG29208@dhcp22.suse.cz> <5864D6CE.7070001@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5864D6CE.7070001@samsung.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3461 Lines: 107 On Thu 29-12-16 18:26:38, Jaewon Kim wrote: > > > On 2016년 12월 29일 18:14, Michal Hocko wrote: > > On Thu 29-12-16 11:28:02, Jaewon Kim wrote: > >> There are many reasons of CMA allocation failure such as EBUSY, ENOMEM, EINTR. > >> This patch prints the error value and bitmap status to know available pages > >> regarding fragmentation. > >> > >> This is an ENOMEM example with this patch. > >> [ 11.616321] [2: Binder:711_1: 740] cma: cma_alloc: alloc failed, req-size: 256 pages, ret: -12 > >> [ 11.616365] [2: Binder:711_1: 740] number of available pages: 4+7+7+8+38+166+127=>357 pages, total: 2048 pages > > Could you be more specific why this part is useful? > Hi > Without this patch we do not know why CMA allocation failed. Yes, I understand the first part > Additionally in case of ENOMEM, with bitmap status we can figure out that The code doesn't seem to check for ENOMEM though > if it is too small CMA region issue or if it is fragmentation issue. then please describe that in the changelog. If I got it right the above would tell us that the fragmentation is the problem, right? > > > >> Signed-off-by: Jaewon Kim > >> --- > >> mm/cma.c | 29 ++++++++++++++++++++++++++++- > >> 1 file changed, 28 insertions(+), 1 deletion(-) > >> > >> diff --git a/mm/cma.c b/mm/cma.c > >> index c960459..535aa39 100644 > >> --- a/mm/cma.c > >> +++ b/mm/cma.c > >> @@ -369,7 +369,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align) > >> unsigned long start = 0; > >> unsigned long bitmap_maxno, bitmap_no, bitmap_count; > >> struct page *page = NULL; > >> - int ret; > >> + int ret = -ENOMEM; > >> > >> if (!cma || !cma->count) > >> return NULL; > >> @@ -427,6 +427,33 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align) > >> trace_cma_alloc(pfn, page, count, align); > >> > >> pr_debug("%s(): returned %p\n", __func__, page); > >> + > >> + if (ret != 0) { > >> + unsigned int nr, nr_total = 0; > >> + unsigned long next_set_bit; > >> + > >> + pr_info("%s: alloc failed, req-size: %zu pages, ret: %d\n", > >> + __func__, count, ret); > >> + mutex_lock(&cma->lock); > >> + printk("number of available pages: "); I guess you want pr_info (or maybe pr_debug) here > >> + start = 0; > >> + for (;;) { > >> + bitmap_no = find_next_zero_bit(cma->bitmap, cma->count, start); > >> + next_set_bit = find_next_bit(cma->bitmap, cma->count, bitmap_no); > >> + nr = next_set_bit - bitmap_no; > >> + if (bitmap_no >= cma->count) > >> + break; > >> + if (nr_total == 0) > >> + printk("%u", nr); > >> + else > >> + printk("+%u", nr); pr_cont > >> + nr_total += nr; > >> + start = bitmap_no + nr; > >> + } > >> + printk("=>%u pages, total: %lu pages\n", nr_total, cma->count); pr_cont > >> + mutex_unlock(&cma->lock); > >> + } > >> + > >> return page; > >> } > >> > >> -- > >> 1.9.1 > >> > >> -- > >> 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/ . > >> Don't email: email@kvack.org > > -- > 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/ . > Don't email: email@kvack.org -- Michal Hocko SUSE Labs