[lttng-dev] [PATCH 1/3] Add default subbuf sizes getter functions.
Simon Marchi
simon.marchi at polymtl.ca
Sun Nov 11 23:36:03 EST 2012
Hi David,
I just sent my v2 for this patch. I changed the logic so that it still
uses the DEFAULT_*_SUBBUF_SIZE defines, but check that it is >= page
size. It should answer your first two comments/questions.
I don't think it would help to put these inline, since they are only
called in slow paths.
Simon
> Hi Simon,
>
> Can you please rename the get_default_* function family to default_get_*
> in order to respect the name spacing of files.
>
> Comment below:
>
> Simon Marchi:
>> This patch adds src/common/defaults.c file. It contains functions to
>> retrieve defaults subbuf sizes based on the architecture page size.
>>
>> Signed-off-by: Simon Marchi <simon.marchi at polymtl.ca>
>> ---
>> src/common/Makefile.am | 2 +-
>> src/common/defaults.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++
>> src/common/defaults.h | 7 ++++
>> 3 files changed, 94 insertions(+), 1 deletions(-)
>> create mode 100644 src/common/defaults.c
>>
>> diff --git a/src/common/Makefile.am b/src/common/Makefile.am
>> index b43b376..f91259c 100644
>> --- a/src/common/Makefile.am
>> +++ b/src/common/Makefile.am
>> @@ -12,7 +12,7 @@ noinst_HEADERS = lttng-kernel.h defaults.h macros.h error.h futex.h \
>> noinst_LTLIBRARIES = libcommon.la
>>
>> libcommon_la_SOURCES = error.h error.c utils.c utils.h runas.c runas.h \
>> - common.h futex.c futex.h uri.c uri.h
>> + common.h futex.c futex.h uri.c uri.h defaults.c
>>
>> # Consumer library
>> noinst_LTLIBRARIES += libconsumer.la
>> diff --git a/src/common/defaults.c b/src/common/defaults.c
>> new file mode 100644
>> index 0000000..48d6605
>> --- /dev/null
>> +++ b/src/common/defaults.c
>> @@ -0,0 +1,86 @@
>> +/*
>> + * Copyright (C) 2012 - Simon Marchi <simon.marchi at polymtl.ca>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License, version 2 only,
>> + * as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful, but WITHOUT
>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
>> + * more details.
>> + *
>> + * You should have received a copy of the GNU General Public License along
>> + * with this program; if not, write to the Free Software Foundation, Inc.,
>> + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
>> + */
>> +
>> +#include <stddef.h>
>> +#include <unistd.h>
>> +
>> +#include "defaults.h"
>> +
>> +static size_t default_channel_subbuf_size;
>> +static size_t default_metadata_subbuf_size;
>> +static size_t default_kernel_channel_subbuf_size;
>> +static size_t default_ust_channel_subbuf_size;
>> +
>> +static void __attribute__((constructor)) init_defaults(void)
>> +{
>> + default_kernel_channel_subbuf_size = DEFAULT_KERNEL_CHANNEL_SUBBUF_SIZE;
>
> Why is the kernel getting a default value and not a page size ?
>
>> +
>> + long page_size = sysconf(_SC_PAGESIZE);
>> + if (page_size > 0) {
>> + default_channel_subbuf_size = page_size;
>> + default_metadata_subbuf_size = page_size;
>> + default_ust_channel_subbuf_size = page_size;
>> + } else {
>> + default_channel_subbuf_size = 4096;
>> + default_metadata_subbuf_size = 4096;
>> + default_ust_channel_subbuf_size = 4096;
>
> Should we use a default value for this 4096 size here with a
> DEFINE_*_SUBBUF_SIZE or... ?
>
> Seems a bit odd that the kernel got a default define value but not UST
> and metadata.
>
>> + }
>> +}
>> +
>> +/*
>> + * Returns the default subbuf size.
>> + *
>> + * This function depends on a value that is set at constructor time, so it is
>> + * unsafe to call it from another constructor.
>> + */
>> +size_t get_default_channel_subbuf_size(void)
>> +{
>> + return default_channel_subbuf_size;
>> +}
>> +
>> +/*
>> + * Returns the default metadata subbuf size.
>> + *
>> + * This function depends on a value that is set at constructor time, so it is
>> + * unsafe to call it from another constructor.
>> + */
>> +size_t get_default_metadata_subbuf_size(void)
>> +{
>> + return default_metadata_subbuf_size;
>> +}
>> +
>> +/*
>> + * Returns the default subbuf size for the kernel domain.
>> + *
>> + * This function depends on a value that is set at constructor time, so it is
>> + * unsafe to call it from another constructor.
>> + */
>> +size_t get_default_kernel_channel_subbuf_size(void)
>> +{
>> + return default_kernel_channel_subbuf_size;
>> +}
>> +
>> +/*
>> + * Returns the default subbuf size for the UST domain.
>> + *
>> + * This function depends on a value that is set at constructor time, so it is
>> + * unsafe to call it from another constructor.
>> + */
>> +size_t get_default_ust_channel_subbuf_size(void)
>> +{
>> + return default_ust_channel_subbuf_size;
>> +}
>
> I'm wondering if all these functions should be static inline in the
> default.h...
>
> Thoughts?
>
> Otherwise, the patch looks good!
>
> Thanks
> David
>
>> diff --git a/src/common/defaults.h b/src/common/defaults.h
>> index 0c0b6ac..efff43e 100644
>> --- a/src/common/defaults.h
>> +++ b/src/common/defaults.h
>> @@ -109,6 +109,9 @@
>> #define DEFAULT_METADATA_SUBBUF_SIZE 4096
>> #define DEFAULT_METADATA_SUBBUF_NUM 2
>>
>> +size_t get_default_channel_subbuf_size(void);
>> +size_t get_default_metadata_subbuf_size(void);
>> +
>> /* Kernel has different defaults */
>>
>> /* DEFAULT_KERNEL_CHANNEL_SUBBUF_SIZE must always be a power of 2 */
>> @@ -121,6 +124,8 @@
>> /* See lttng-kernel.h enum lttng_kernel_output for channel output */
>> #define DEFAULT_KERNEL_CHANNEL_OUTPUT LTTNG_EVENT_SPLICE
>>
>> +size_t get_default_kernel_channel_subbuf_size(void);
>> +
>> /* User space defaults */
>>
>> /* Must be a power of 2 */
>> @@ -130,6 +135,8 @@
>> /* See lttng-ust.h enum lttng_ust_output */
>> #define DEFAULT_UST_CHANNEL_OUTPUT LTTNG_EVENT_MMAP
>>
>> +size_t get_default_ust_channel_subbuf_size(void);
>> +
>> /*
>> * Default timeout value for the sem_timedwait() call. Blocking forever is not
>> * wanted so a timeout is used to control the data flow and not freeze the
>
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