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Date: Thu, 6 Sep 2018 14:50:56 +0300 From: Alexey Budankov <alexey.budankov@...ux.intel.com> To: Jiri Olsa <jolsa@...hat.com> Cc: Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Namhyung Kim <namhyung@...nel.org>, Andi Kleen <ak@...ux.intel.com>, linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v7 1/2]: perf util: map data buffer for preserving collected data On 06.09.2018 14:04, Jiri Olsa wrote: > On Wed, Sep 05, 2018 at 10:19:56AM +0300, Alexey Budankov wrote: >> >> The map->data buffers are used to preserve map->base profiling data >> for writing to disk. AIO map->cblocks are used to queue corresponding >> map->data buffers for asynchronous writing. map->cblocks objects are >> located in the last page of every map->data buffer. >> >> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com> >> --- >> Changes in v7: >> - implemented handling record.aio setting from perfconfig file >> Changes in v6: >> - adjusted setting of priorities for cblocks; >> Changes in v5: >> - reshaped layout of data structures; >> - implemented --aio option; >> Changes in v4: >> - converted mmap()/munmap() to malloc()/free() for mmap->data buffer management >> Changes in v2: >> - converted zalloc() to calloc() for allocation of mmap_aio array, >> - cleared typo and adjusted fallback branch code; >> --- >> tools/perf/builtin-record.c | 15 ++++++++++++- >> tools/perf/perf.h | 1 + >> tools/perf/util/evlist.c | 7 +++--- >> tools/perf/util/evlist.h | 3 ++- >> tools/perf/util/mmap.c | 53 +++++++++++++++++++++++++++++++++++++++++++++ >> tools/perf/util/mmap.h | 6 ++++- >> 6 files changed, 79 insertions(+), 6 deletions(-) >> >> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c >> index 22ebeb92ac51..f17a6f9cb1ba 100644 >> --- a/tools/perf/builtin-record.c >> +++ b/tools/perf/builtin-record.c >> @@ -326,7 +326,8 @@ static int record__mmap_evlist(struct record *rec, >> >> if (perf_evlist__mmap_ex(evlist, opts->mmap_pages, >> opts->auxtrace_mmap_pages, >> - opts->auxtrace_snapshot_mode) < 0) { >> + opts->auxtrace_snapshot_mode, >> + opts->nr_cblocks) < 0) { >> if (errno == EPERM) { >> pr_err("Permission error mapping pages.\n" >> "Consider increasing " >> @@ -1287,6 +1288,8 @@ static int perf_record_config(const char *var, const char *value, void *cb) >> var = "call-graph.record-mode"; >> return perf_default_config(var, value, cb); >> } >> + if (!strcmp(var, "record.aio")) >> + rec->opts.nr_cblocks = strtol(value, NULL, 0); >> >> return 0; >> } >> @@ -1519,6 +1522,7 @@ static struct record record = { >> .default_per_cpu = true, >> }, >> .proc_map_timeout = 500, >> + .nr_cblocks = 2 >> }, >> .tool = { >> .sample = process_sample_event, >> @@ -1678,6 +1682,8 @@ static struct option __record_options[] = { >> "signal"), >> OPT_BOOLEAN(0, "dry-run", &dry_run, >> "Parse options then exit"), >> + OPT_INTEGER(0, "aio", &record.opts.nr_cblocks, >> + "asynchronous trace write operations (min: 1, max: 32, default: 2)"), > > ok, so this got silently added in recent versions and I couldn't > find any justification for it.. why do we use more aio blocks for > single map now? also why the default is 2? Having more blocks may improve thruput from kernel to userspace for cases when we get more data at map->base but the started AIO is not finished yet. That can easily happen between calls of record__mmap_read_evlist(). > > the option should be more specific like 'aio-blocks' ok. > > the change is difficult enough.. we should start simple and add > these additions with proper justification in separate patches Setting default to 1 gives the simplest solution. I could provide justification where spinning at record__aio_sync() becomes the hotspot. > > thanks, > jirka >
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