Re: [PATCH v1] mem_pool: add GIT_TRACE_MEMPOOL support

From: Ben Peart <peartben@gmail.com>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: git@vger.kernel.org, benpeart@microsoft.com
Subject: Re: [PATCH v1] mem_pool: add GIT_TRACE_MEMPOOL support
Date: Thu, 29 Nov 2018 09:09:04 -0500	[thread overview]
Message-ID: <9ce2df67-d698-0372-4770-32659668ab7e@gmail.com> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.1811281036300.41@tvgsbejvaqbjf.bet>

On 11/28/2018 4:37 AM, Johannes Schindelin wrote:
> Hi Ben,
>
> On Tue, 27 Nov 2018, Ben Peart wrote:
>
>> From: Ben Peart <benpeart@microsoft.com>
>>
>> Add tracing around initializing and discarding mempools. In discard report
>> on the amount of memory unused in the current block to help tune setting
>> the initial_size.
>>
>> Signed-off-by: Ben Peart <benpeart@microsoft.com>
>> ---
> Looks good.
>
> My only question: should we also trace calls to _alloc(), _calloc() and
> _combine()?

I was trying to tune the initial size in my use of the mem_pool and so 
found this tracing useful to see how much memory was actually being 
used.  I'm inclined to only add tracing as it is needed rather that 
proactively because we think it _might_ be needed.  I suspect _alloc() 
and _calloc() would get very noisy and not add much value.

>
> Ciao,
> Johannes
>
>> Notes:
>>      Base Ref: * git-trace-mempool
>>      Web-Diff: https://github.com/benpeart/git/commit/9ac84bbca2
>>      Checkout: git fetch https://github.com/benpeart/git git-trace-mempool-v1 && git checkout 9ac84bbca2
>>
>>   mem-pool.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/mem-pool.c b/mem-pool.c
>> index a2841a4a9a..065389aaec 100644
>> --- a/mem-pool.c
>> +++ b/mem-pool.c
>> @@ -5,6 +5,7 @@
>>   #include "cache.h"
>>   #include "mem-pool.h"
>>   
>> +static struct trace_key trace_mem_pool = TRACE_KEY_INIT(MEMPOOL);
>>   #define BLOCK_GROWTH_SIZE 1024*1024 - sizeof(struct mp_block);
>>   
>>   /*
>> @@ -48,12 +49,16 @@ void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size)
>>   		mem_pool_alloc_block(pool, initial_size, NULL);
>>   
>>   	*mem_pool = pool;
>> +	trace_printf_key(&trace_mem_pool, "mem_pool (%p): init (%"PRIuMAX") initial size\n",
>> +		pool, (uintmax_t)initial_size);
>>   }
>>   
>>   void mem_pool_discard(struct mem_pool *mem_pool, int invalidate_memory)
>>   {
>>   	struct mp_block *block, *block_to_free;
>>   
>> +	trace_printf_key(&trace_mem_pool, "mem_pool (%p): discard (%"PRIuMAX") unused\n",
>> +		mem_pool, (uintmax_t)(mem_pool->mp_block->end - mem_pool->mp_block->next_free));
>>   	block = mem_pool->mp_block;
>>   	while (block)
>>   	{
>>
>> base-commit: bb75be6cb916297f271c846f2f9caa3daaaec718
>> -- 
>> 2.18.0.windows.1
>>
>>