Re: [PATCH v2] lib: sparse: allocate FASTBOOT_MAX_BLK_WRITE instead of small number

[Mattijs Korpershoek <mkorpershoek@baylibre.com>]

Hi Qianfan,

Thank you for your review.

On ven., juil. 07, 2023 at 18:54, qianfan <qianfanguijin@163.com> wrote:

> 在 2023/7/7 16:13, Mattijs Korpershoek 写道:
>> Commit 62649165cb02 ("lib: sparse: Make CHUNK_TYPE_RAW buffer aligned")
>> fixed cache alignment for systems with a D-CACHE.
>>
>> However it introduced some performance regressions [1] on system
>> flashing huge images, such as Android.
>>
>> On AM62x SK EVM, we also observe such performance penalty:
>> Sending sparse 'super' 1/2 (768793 KB)             OKAY [ 23.954s]
>> Writing 'super'                                    OKAY [ 75.926s]
>> Sending sparse 'super' 2/2 (629819 KB)             OKAY [ 19.641s]
>> Writing 'super'                                    OKAY [ 62.849s]
>> Finished. Total time: 182.474s
>>
>> The reason for this is that we use an arbitrary small buffer
>> (info->blksz * 100) for transferring.
>>
>> Fix it by using a bigger buffer (info->blksz * FASTBOOT_MAX_BLK_WRITE)
>> as suggested in the original's patch review [2].
>>
>> With this patch, performance impact is mitigated:
>> Sending sparse 'super' 1/2 (768793 KB)             OKAY [ 23.912s]
>> Writing 'super'                                    OKAY [ 15.780s]
>> Sending sparse 'super' 2/2 (629819 KB)             OKAY [ 19.581s]
>> Writing 'super'                                    OKAY [ 17.192s]
>> Finished. Total time: 76.569s
>>
>> [1] https://lore.kernel.org/r/20221118121323.4009193-1-gary.bisson@boundarydevices.com
>> [2] https://lore.kernel.org/r/all/43e4c17c-4483-ec8e-f843-9b4c5569bd18@seco.com/
>>
>> Fixes: 62649165cb02 ("lib: sparse: Make CHUNK_TYPE_RAW buffer aligned")
>> Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
>> ---
>> Changes in v2:
>> - Use FASTBOOT_MAX_BLK_WRITE instead of blkcnt (Qianfan)
>> - Link to v1: https://lore.kernel.org/r/20230616-sparse-flash-fix-v1-1-6bafeacc567b@baylibre.com
>> ---
>>   drivers/fastboot/fb_mmc.c | 2 --
>>   include/image-sparse.h    | 2 ++
>>   lib/image-sparse.c        | 3 ++-
>>   3 files changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/fastboot/fb_mmc.c b/drivers/fastboot/fb_mmc.c
>> index 9d25c402028a..060918e49109 100644
>> --- a/drivers/fastboot/fb_mmc.c
>> +++ b/drivers/fastboot/fb_mmc.c
>> @@ -19,8 +19,6 @@
>>   #include <linux/compat.h>
>>   #include <android_image.h>
>>   
>> -#define FASTBOOT_MAX_BLK_WRITE 16384
>> -
>>   #define BOOT_PARTITION_NAME "boot"
>>   
>>   struct fb_mmc_sparse {
>> diff --git a/include/image-sparse.h b/include/image-sparse.h
>> index 0572dbd0a283..282a0b256498 100644
>> --- a/include/image-sparse.h
>> +++ b/include/image-sparse.h
>> @@ -7,6 +7,8 @@
>>   #include <part.h>
>>   #include <sparse_format.h>
>>   
>> +#define FASTBOOT_MAX_BLK_WRITE 16384
> Hi:
>
> Just a personal suggestion, define sometings like FASTBOOT_MAX_BLK_WRITE in
> image-sparse.c is very strange.
>
> Or maybe define a marco such as SPARSE_MAX_BLK_WRITE and set a default
> value to 16384, and leave some comments for why we choice this value.

I don't agree with having a duplicating between SPARSE_MAX_BLK_WRITE
and FASTBOOT_MAX_BLK_WRITE. code comments can rot as well.

And FASTBOOT_MAX_BLK_WRITE is used for both sparse and unsparsed image,
which is why I chose to not rename it.

>
> Thanks.
>> +
>>   #define ROUNDUP(x, y)	(((x) + ((y) - 1)) & ~((y) - 1))
>>   
>>   struct sparse_storage {
>> diff --git a/lib/image-sparse.c b/lib/image-sparse.c
>> index 5ec0f94ab3eb..8f8a67e15804 100644
>> --- a/lib/image-sparse.c
>> +++ b/lib/image-sparse.c
>> @@ -55,7 +55,8 @@ static lbaint_t write_sparse_chunk_raw(struct sparse_storage *info,
>>   				       void *data,
>>   				       char *response)
>>   {
>> -	lbaint_t n = blkcnt, write_blks, blks = 0, aligned_buf_blks = 100;
>> +	lbaint_t n = blkcnt, write_blks, blks = 0;
>> +	lbaint_t aligned_buf_blks = FASTBOOT_MAX_BLK_WRITE;
>>   	uint32_t *aligned_buf = NULL;
>>   
>>   	if (CONFIG_IS_ENABLED(SYS_DCACHE_OFF)) {
>>
>> ---
>> base-commit: 923de765ee1a5b26310f02cb42dcbad9e2b011c5
>> change-id: 20230616-sparse-flash-fix-9c2852aa8d16
>>
>> Best regards,