From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5697BC433EF for ; Tue, 28 Jun 2022 14:53:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347464AbiF1Oxh (ORCPT ); Tue, 28 Jun 2022 10:53:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347444AbiF1Oxe (ORCPT ); Tue, 28 Jun 2022 10:53:34 -0400 Received: from mail-lf1-x129.google.com (mail-lf1-x129.google.com [IPv6:2a00:1450:4864:20::129]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDEFCE19 for ; Tue, 28 Jun 2022 07:53:07 -0700 (PDT) Received: by mail-lf1-x129.google.com with SMTP id z21so22700340lfb.12 for ; Tue, 28 Jun 2022 07:53:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=YTlupDxR0VuIlLuxHDuN5QQVbAsill4fsciLPt4itQQ=; b=CK+v3yJgQ6tqQ6GDj03fYUW2dSNd/lPiUr2/BoPpFuw76C7+8vo6ZiXT7YBCj+y0BX I8rPJGnGimDE+jY5GN+SXOoMAXMozLWKwSAHu2kVTE/9KyQ2S0/2Y9u2ZI5GNCLZqf63 ROjWdqrK+0mlaO/QmzEZWTqhfv03RSKOp6ZWWBugRAMKFpvDRfz3wbDAF3Jlt4VLNQiK qyX+0r5YBMz3rdZeuU7U1AZHOdH6V1elOMC1LsqXZnGW4Li7eeVVqQHZ85SQnwuQgsJR 5FNm51BQjf+ru4edKuxfPbmSFpAK9ULRaCqsALBctVOe2vPi8iFXwhQLGbofAg3npGeN kGRw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=YTlupDxR0VuIlLuxHDuN5QQVbAsill4fsciLPt4itQQ=; b=g7eHQielXP1VnjM3MvdwGY+hkXLy7O6y/AdvcY97hkLntqyj8KvfEr0fLtsM7GcT46 pV0n2GhCTbVA7Tv9BFRxPqyjWs4m6Y1bWkt5755KPVTlnPeKiCPBx8SwlUYlAiXS6bjV cCEfGvd7nF20rwD+gbl6snjh/oLn+M9QZ511mNAqPPkbUSpD1fc/aKHAca7BAFdQZVNy IfQ68Bpko3RkaQ3gVdBKLhMdmDeLq/E+nmPvFbOza8CBR7c/RLz517Bs7/q6/gP6FL7q jn5Yx5NesoP1mR2ijRSbuneSARSmUrx5FUai6wgSFY0d8MUZaH1wNZyeCU9r+fUI+HLj +o0Q== X-Gm-Message-State: AJIora/oeR+rN0wmjRzjf3aiPZQShcZLrxj3r67CXDjGVFYS6a3oJXO1 p1MZ/KQMgwK2D3UinqNJATNqhr1ikafmpO8Cz69DAw== X-Google-Smtp-Source: AGRyM1vkpEV6l5ncNBuwoJTHSw7hdq0PUPHxE7ZvWBHFWAQusvLqPE8bfvDu0rO5nfpTbV2ylARwqgHtko8nyWD1E0w= X-Received: by 2002:a05:6512:39ce:b0:481:31e4:1e06 with SMTP id k14-20020a05651239ce00b0048131e41e06mr2071928lfu.376.1656427985930; Tue, 28 Jun 2022 07:53:05 -0700 (PDT) MIME-Version: 1.0 References: <20220628095833.2579903-1-elver@google.com> <20220628095833.2579903-12-elver@google.com> In-Reply-To: <20220628095833.2579903-12-elver@google.com> From: Dmitry Vyukov Date: Tue, 28 Jun 2022 16:52:54 +0200 Message-ID: Subject: Re: [PATCH v2 11/13] perf/hw_breakpoint: Introduce bp_slots_histogram To: Marco Elver Cc: Peter Zijlstra , Frederic Weisbecker , Ingo Molnar , Thomas Gleixner , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-perf-users@vger.kernel.org, x86@kernel.org, linux-sh@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org On Tue, 28 Jun 2022 at 11:59, Marco Elver wrote: > > Factor out the existing `atomic_t count[N]` into its own struct called > 'bp_slots_histogram', to generalize and make its intent clearer in > preparation of reusing elsewhere. The basic idea of bucketing "total > uses of N slots" resembles a histogram, so calling it such seems most > intuitive. > > No functional change. > > Signed-off-by: Marco Elver Reviewed-by: Dmitry Vyukov > --- > v2: > * New patch. > --- > kernel/events/hw_breakpoint.c | 94 +++++++++++++++++++++++------------ > 1 file changed, 62 insertions(+), 32 deletions(-) > > diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c > index 128ba3429223..18886f115abc 100644 > --- a/kernel/events/hw_breakpoint.c > +++ b/kernel/events/hw_breakpoint.c > @@ -36,19 +36,27 @@ > #include > > /* > - * Constraints data > + * Datastructure to track the total uses of N slots across tasks or CPUs; > + * bp_slots_histogram::count[N] is the number of assigned N+1 breakpoint slots. > */ > -struct bp_cpuinfo { > - /* Number of pinned cpu breakpoints in a cpu */ > - unsigned int cpu_pinned; > - /* tsk_pinned[n] is the number of tasks having n+1 breakpoints */ > +struct bp_slots_histogram { > #ifdef hw_breakpoint_slots > - atomic_t tsk_pinned[hw_breakpoint_slots(0)]; > + atomic_t count[hw_breakpoint_slots(0)]; > #else > - atomic_t *tsk_pinned; > + atomic_t *count; > #endif > }; > > +/* > + * Per-CPU constraints data. > + */ > +struct bp_cpuinfo { > + /* Number of pinned CPU breakpoints in a CPU. */ > + unsigned int cpu_pinned; > + /* Histogram of pinned task breakpoints in a CPU. */ > + struct bp_slots_histogram tsk_pinned; > +}; > + > static DEFINE_PER_CPU(struct bp_cpuinfo, bp_cpuinfo[TYPE_MAX]); > > static struct bp_cpuinfo *get_bp_info(int cpu, enum bp_type_idx type) > @@ -159,6 +167,18 @@ static inline int hw_breakpoint_slots_cached(int type) > return __nr_bp_slots[type]; > } > > +static __init bool > +bp_slots_histogram_alloc(struct bp_slots_histogram *hist, enum bp_type_idx type) > +{ > + hist->count = kcalloc(hw_breakpoint_slots_cached(type), sizeof(*hist->count), GFP_KERNEL); > + return hist->count; > +} > + > +static __init void bp_slots_histogram_free(struct bp_slots_histogram *hist) > +{ > + kfree(hist->count); > +} > + > static __init int init_breakpoint_slots(void) > { > int i, cpu, err_cpu; > @@ -170,8 +190,7 @@ static __init int init_breakpoint_slots(void) > for (i = 0; i < TYPE_MAX; i++) { > struct bp_cpuinfo *info = get_bp_info(cpu, i); > > - info->tsk_pinned = kcalloc(__nr_bp_slots[i], sizeof(atomic_t), GFP_KERNEL); > - if (!info->tsk_pinned) > + if (!bp_slots_histogram_alloc(&info->tsk_pinned, i)) > goto err; > } > } > @@ -180,7 +199,7 @@ static __init int init_breakpoint_slots(void) > err: > for_each_possible_cpu(err_cpu) { > for (i = 0; i < TYPE_MAX; i++) > - kfree(get_bp_info(err_cpu, i)->tsk_pinned); > + bp_slots_histogram_free(&get_bp_info(err_cpu, i)->tsk_pinned); > if (err_cpu == cpu) > break; > } > @@ -189,6 +208,34 @@ static __init int init_breakpoint_slots(void) > } > #endif > > +static inline void > +bp_slots_histogram_add(struct bp_slots_histogram *hist, int old, int val) > +{ > + const int old_idx = old - 1; > + const int new_idx = old_idx + val; > + > + if (old_idx >= 0) > + atomic_dec(&hist->count[old_idx]); > + if (new_idx >= 0) > + atomic_inc(&hist->count[new_idx]); > +} > + > +static int > +bp_slots_histogram_max(struct bp_slots_histogram *hist, enum bp_type_idx type) > +{ > + for (int i = hw_breakpoint_slots_cached(type) - 1; i >= 0; i--) { > + const int count = atomic_read(&hist->count[i]); > + > + /* Catch unexpected writers; we want a stable snapshot. */ > + ASSERT_EXCLUSIVE_WRITER(hist->count[i]); > + if (count > 0) > + return i + 1; > + WARN(count < 0, "inconsistent breakpoint slots histogram"); > + } > + > + return 0; > +} > + > #ifndef hw_breakpoint_weight > static inline int hw_breakpoint_weight(struct perf_event *bp) > { > @@ -205,13 +252,11 @@ static inline enum bp_type_idx find_slot_idx(u64 bp_type) > } > > /* > - * Report the maximum number of pinned breakpoints a task > - * have in this cpu > + * Return the maximum number of pinned breakpoints a task has in this CPU. > */ > static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type) > { > - atomic_t *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned; > - int i; > + struct bp_slots_histogram *tsk_pinned = &get_bp_info(cpu, type)->tsk_pinned; > > /* > * At this point we want to have acquired the bp_cpuinfo_sem as a > @@ -219,14 +264,7 @@ static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type) > * toggle_bp_task_slot() to tsk_pinned, and we get a stable snapshot. > */ > lockdep_assert_held_write(&bp_cpuinfo_sem); > - > - for (i = hw_breakpoint_slots_cached(type) - 1; i >= 0; i--) { > - ASSERT_EXCLUSIVE_WRITER(tsk_pinned[i]); /* Catch unexpected writers. */ > - if (atomic_read(&tsk_pinned[i]) > 0) > - return i + 1; > - } > - > - return 0; > + return bp_slots_histogram_max(tsk_pinned, type); > } > > /* > @@ -300,8 +338,7 @@ max_bp_pinned_slots(struct perf_event *bp, enum bp_type_idx type) > static void toggle_bp_task_slot(struct perf_event *bp, int cpu, > enum bp_type_idx type, int weight) > { > - atomic_t *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned; > - int old_idx, new_idx; > + struct bp_slots_histogram *tsk_pinned = &get_bp_info(cpu, type)->tsk_pinned; > > /* > * If bp->hw.target, tsk_pinned is only modified, but not used > @@ -311,14 +348,7 @@ static void toggle_bp_task_slot(struct perf_event *bp, int cpu, > * bp_cpuinfo_sem as a writer to stabilize tsk_pinned's value. > */ > lockdep_assert_held_read(&bp_cpuinfo_sem); > - > - old_idx = task_bp_pinned(cpu, bp, type) - 1; > - new_idx = old_idx + weight; > - > - if (old_idx >= 0) > - atomic_dec(&tsk_pinned[old_idx]); > - if (new_idx >= 0) > - atomic_inc(&tsk_pinned[new_idx]); > + bp_slots_histogram_add(tsk_pinned, task_bp_pinned(cpu, bp, type), weight); > } > > /* > -- > 2.37.0.rc0.161.g10f37bed90-goog > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EC9BFC43334 for ; Tue, 28 Jun 2022 14:53:46 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4LXSK52wDZz3dxx for ; Wed, 29 Jun 2022 00:53:45 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; 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Tue, 28 Jun 2022 07:53:05 -0700 (PDT) MIME-Version: 1.0 References: <20220628095833.2579903-1-elver@google.com> <20220628095833.2579903-12-elver@google.com> In-Reply-To: <20220628095833.2579903-12-elver@google.com> From: Dmitry Vyukov Date: Tue, 28 Jun 2022 16:52:54 +0200 Message-ID: Subject: Re: [PATCH v2 11/13] perf/hw_breakpoint: Introduce bp_slots_histogram To: Marco Elver Content-Type: text/plain; charset="UTF-8" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , linux-sh@vger.kernel.org, Peter Zijlstra , Frederic Weisbecker , x86@kernel.org, linuxppc-dev@lists.ozlabs.org, Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Alexander Shishkin , kasan-dev@googlegroups.com, Namhyung Kim , Thomas Gleixner , Jiri Olsa , Ingo Molnar Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, 28 Jun 2022 at 11:59, Marco Elver wrote: > > Factor out the existing `atomic_t count[N]` into its own struct called > 'bp_slots_histogram', to generalize and make its intent clearer in > preparation of reusing elsewhere. The basic idea of bucketing "total > uses of N slots" resembles a histogram, so calling it such seems most > intuitive. > > No functional change. > > Signed-off-by: Marco Elver Reviewed-by: Dmitry Vyukov > --- > v2: > * New patch. > --- > kernel/events/hw_breakpoint.c | 94 +++++++++++++++++++++++------------ > 1 file changed, 62 insertions(+), 32 deletions(-) > > diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c > index 128ba3429223..18886f115abc 100644 > --- a/kernel/events/hw_breakpoint.c > +++ b/kernel/events/hw_breakpoint.c > @@ -36,19 +36,27 @@ > #include > > /* > - * Constraints data > + * Datastructure to track the total uses of N slots across tasks or CPUs; > + * bp_slots_histogram::count[N] is the number of assigned N+1 breakpoint slots. > */ > -struct bp_cpuinfo { > - /* Number of pinned cpu breakpoints in a cpu */ > - unsigned int cpu_pinned; > - /* tsk_pinned[n] is the number of tasks having n+1 breakpoints */ > +struct bp_slots_histogram { > #ifdef hw_breakpoint_slots > - atomic_t tsk_pinned[hw_breakpoint_slots(0)]; > + atomic_t count[hw_breakpoint_slots(0)]; > #else > - atomic_t *tsk_pinned; > + atomic_t *count; > #endif > }; > > +/* > + * Per-CPU constraints data. > + */ > +struct bp_cpuinfo { > + /* Number of pinned CPU breakpoints in a CPU. */ > + unsigned int cpu_pinned; > + /* Histogram of pinned task breakpoints in a CPU. */ > + struct bp_slots_histogram tsk_pinned; > +}; > + > static DEFINE_PER_CPU(struct bp_cpuinfo, bp_cpuinfo[TYPE_MAX]); > > static struct bp_cpuinfo *get_bp_info(int cpu, enum bp_type_idx type) > @@ -159,6 +167,18 @@ static inline int hw_breakpoint_slots_cached(int type) > return __nr_bp_slots[type]; > } > > +static __init bool > +bp_slots_histogram_alloc(struct bp_slots_histogram *hist, enum bp_type_idx type) > +{ > + hist->count = kcalloc(hw_breakpoint_slots_cached(type), sizeof(*hist->count), GFP_KERNEL); > + return hist->count; > +} > + > +static __init void bp_slots_histogram_free(struct bp_slots_histogram *hist) > +{ > + kfree(hist->count); > +} > + > static __init int init_breakpoint_slots(void) > { > int i, cpu, err_cpu; > @@ -170,8 +190,7 @@ static __init int init_breakpoint_slots(void) > for (i = 0; i < TYPE_MAX; i++) { > struct bp_cpuinfo *info = get_bp_info(cpu, i); > > - info->tsk_pinned = kcalloc(__nr_bp_slots[i], sizeof(atomic_t), GFP_KERNEL); > - if (!info->tsk_pinned) > + if (!bp_slots_histogram_alloc(&info->tsk_pinned, i)) > goto err; > } > } > @@ -180,7 +199,7 @@ static __init int init_breakpoint_slots(void) > err: > for_each_possible_cpu(err_cpu) { > for (i = 0; i < TYPE_MAX; i++) > - kfree(get_bp_info(err_cpu, i)->tsk_pinned); > + bp_slots_histogram_free(&get_bp_info(err_cpu, i)->tsk_pinned); > if (err_cpu == cpu) > break; > } > @@ -189,6 +208,34 @@ static __init int init_breakpoint_slots(void) > } > #endif > > +static inline void > +bp_slots_histogram_add(struct bp_slots_histogram *hist, int old, int val) > +{ > + const int old_idx = old - 1; > + const int new_idx = old_idx + val; > + > + if (old_idx >= 0) > + atomic_dec(&hist->count[old_idx]); > + if (new_idx >= 0) > + atomic_inc(&hist->count[new_idx]); > +} > + > +static int > +bp_slots_histogram_max(struct bp_slots_histogram *hist, enum bp_type_idx type) > +{ > + for (int i = hw_breakpoint_slots_cached(type) - 1; i >= 0; i--) { > + const int count = atomic_read(&hist->count[i]); > + > + /* Catch unexpected writers; we want a stable snapshot. */ > + ASSERT_EXCLUSIVE_WRITER(hist->count[i]); > + if (count > 0) > + return i + 1; > + WARN(count < 0, "inconsistent breakpoint slots histogram"); > + } > + > + return 0; > +} > + > #ifndef hw_breakpoint_weight > static inline int hw_breakpoint_weight(struct perf_event *bp) > { > @@ -205,13 +252,11 @@ static inline enum bp_type_idx find_slot_idx(u64 bp_type) > } > > /* > - * Report the maximum number of pinned breakpoints a task > - * have in this cpu > + * Return the maximum number of pinned breakpoints a task has in this CPU. > */ > static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type) > { > - atomic_t *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned; > - int i; > + struct bp_slots_histogram *tsk_pinned = &get_bp_info(cpu, type)->tsk_pinned; > > /* > * At this point we want to have acquired the bp_cpuinfo_sem as a > @@ -219,14 +264,7 @@ static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type) > * toggle_bp_task_slot() to tsk_pinned, and we get a stable snapshot. > */ > lockdep_assert_held_write(&bp_cpuinfo_sem); > - > - for (i = hw_breakpoint_slots_cached(type) - 1; i >= 0; i--) { > - ASSERT_EXCLUSIVE_WRITER(tsk_pinned[i]); /* Catch unexpected writers. */ > - if (atomic_read(&tsk_pinned[i]) > 0) > - return i + 1; > - } > - > - return 0; > + return bp_slots_histogram_max(tsk_pinned, type); > } > > /* > @@ -300,8 +338,7 @@ max_bp_pinned_slots(struct perf_event *bp, enum bp_type_idx type) > static void toggle_bp_task_slot(struct perf_event *bp, int cpu, > enum bp_type_idx type, int weight) > { > - atomic_t *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned; > - int old_idx, new_idx; > + struct bp_slots_histogram *tsk_pinned = &get_bp_info(cpu, type)->tsk_pinned; > > /* > * If bp->hw.target, tsk_pinned is only modified, but not used > @@ -311,14 +348,7 @@ static void toggle_bp_task_slot(struct perf_event *bp, int cpu, > * bp_cpuinfo_sem as a writer to stabilize tsk_pinned's value. > */ > lockdep_assert_held_read(&bp_cpuinfo_sem); > - > - old_idx = task_bp_pinned(cpu, bp, type) - 1; > - new_idx = old_idx + weight; > - > - if (old_idx >= 0) > - atomic_dec(&tsk_pinned[old_idx]); > - if (new_idx >= 0) > - atomic_inc(&tsk_pinned[new_idx]); > + bp_slots_histogram_add(tsk_pinned, task_bp_pinned(cpu, bp, type), weight); > } > > /* > -- > 2.37.0.rc0.161.g10f37bed90-goog >