Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751259Ab0HJEdQ (ORCPT ); Tue, 10 Aug 2010 00:33:16 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:53190 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750838Ab0HJEdJ (ORCPT ); Tue, 10 Aug 2010 00:33:09 -0400 Date: Mon, 9 Aug 2010 21:34:31 -0700 From: Andrew Morton To: Nitin Gupta Cc: Pekka Enberg , Minchan Kim , Greg KH , Linux Driver Project , linux-mm , linux-kernel Subject: Re: [PATCH 03/10] Use percpu stats Message-Id: <20100809213431.d7699d46.akpm@linux-foundation.org> In-Reply-To: <1281374816-904-4-git-send-email-ngupta@vflare.org> References: <1281374816-904-1-git-send-email-ngupta@vflare.org> <1281374816-904-4-git-send-email-ngupta@vflare.org> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1312 Lines: 45 On Mon, 9 Aug 2010 22:56:49 +0530 Nitin Gupta wrote: > +/* > + * Individual percpu values can go negative but the sum across all CPUs > + * must always be positive (we store various counts). So, return sum as > + * unsigned value. > + */ > +static u64 zram_get_stat(struct zram *zram, enum zram_stats_index idx) > { > - u64 val; > - > - spin_lock(&zram->stat64_lock); > - val = *v; > - spin_unlock(&zram->stat64_lock); > + int cpu; > + s64 val = 0; > + > + for_each_possible_cpu(cpu) { > + s64 temp; > + unsigned int start; > + struct zram_stats_cpu *stats; > + > + stats = per_cpu_ptr(zram->stats, cpu); > + do { > + start = u64_stats_fetch_begin(&stats->syncp); > + temp = stats->count[idx]; > + } while (u64_stats_fetch_retry(&stats->syncp, start)); > + val += temp; > + } > > + WARN_ON(val < 0); > return val; > } That reimplements include/linux/percpu_counter.h, poorly. Please see the June discussion "[PATCH v2 1/2] tmpfs: Quick token library to allow scalable retrieval of tokens from token jar" for some discussion. -- 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/