On 9/24/25 14:53, wangzijie wrote:
>> On 9/24/25 13:58, Yunji Kang wrote:
>>> In f2fs_precache_extents(), For large files, It requires reading many
>>> node blocks. Instead of reading each node block with synchronous I/O,
>>> this patch applies readahead so that node blocks can be fetched in
>>> advance.
>>>
>>> It reduces the overhead of repeated sync reads and improves efficiency
>>> when precaching extents of large files.
>>>
>>> I created a file with the same largest extent and executed the test.
>>> For this experiment, I set the file's largest extent with an offset of 0
>>> and a size of 1GB. I configured the remaining area with 100MB extents.
>>>
>>> 5GB test file:
>>> dd if=/dev/urandom of=test1 bs=1m count=5120
>>> cp test1 test2
>>> fsync test1
>>> dd if=test1 of=test2 bs=1m skip=1024 seek=1024 count=100 conv=notrunc
>>> dd if=test1 of=test2 bs=1m skip=1224 seek=1224 count=100 conv=notrunc
>>> ...
>>> dd if=test1 of=test2 bs=1m skip=5024 seek=5024 count=100 conv=notrunc
>>> reboot
>>>
>>> I also created 10GB and 20GB files with large extents using the same
>>> method.
>>>
>>> ioctl(F2FS_IOC_PRECACHE_EXTENTS) test results are as follows:
>>> +-----------+---------+---------+-----------+
>>> | File size | Before | After | Reduction |
>>> +-----------+---------+---------+-----------+
>>> | 5GB | 101.8ms | 37.0ms | 72.1% |
>>> | 10GB | 222.9ms | 56.0ms | 74.9% |
>>> | 20GB | 446.2ms | 116.4ms | 73.9% |
>>> +-----------+---------+---------+-----------+
>>> Tested on a 256GB mobile device with an SM8750 chipset.
>>>
>>> Reviewed-by: Sungjong Seo <[email protected]>
>>> Reviewed-by: Sunmin Jeong <[email protected]>
>>> Signed-off-by: Yunji Kang <[email protected]>
>>> ---
>>> v2:
>>> - Modify the readahead condition check routine for better code
>>> readability.
>>> - Update the title from 'node block' to 'node blocks'.
>>>
>>> v3:
>>> - Bug fix to allow more node pages to be readahead.
>>> - Updated with test results.
>>>
>>> fs/f2fs/data.c | 3 +++
>>> fs/f2fs/f2fs.h | 1 +
>>> fs/f2fs/node.c | 4 +++-
>>> 3 files changed, 7 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index 7961e0ddfca3..ab3117e3b24a 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -1572,6 +1572,9 @@ int f2fs_map_blocks(struct inode *inode, struct
>>> f2fs_map_blocks *map, int flag)
>>> pgofs = (pgoff_t)map->m_lblk;
>>> end = pgofs + maxblocks;
>>>
>>> + if (flag == F2FS_GET_BLOCK_PRECACHE)
>>> + mode = LOOKUP_NODE_PRECACHE;
>>
>> If trigger condition of LOOKUP_NODE_RA and LOOKUP_NODE_PRECACHE is the same,
>> What about?
>>
>> if (flag == F2FS_GET_BLOCK_PRECACHE)
>> mode = LOOKUP_NODE_RA;
>>
>> Thanks,
>
> Hi Yunji and Chao,
> I think so, we can directly use LOOKUP_NODE_RA for precache extents.
> BTW, maybe there are more cases that LOOKUP_NODE_RA will be better? Like
> defragment/compress(need to call __f2fs_cluster_blocks() ) ioctl..
Yeah, we can have a try to check the benefits. :)
Thaks,
>
>
>>> +
>>> next_dnode:
>>> if (map->m_may_create) {
>>> if (f2fs_lfs_mode(sbi))
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index 9d3bc9633c1d..3ce41528d48e 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -651,6 +651,7 @@ enum {
>>> * look up a node with readahead called
>>> * by get_data_block.
>>> */
>>> + LOOKUP_NODE_PRECACHE, /* look up a node for
>>> F2FS_GET_BLOCK_PRECACHE */
>>> };
>>>
>>> #define DEFAULT_RETRY_IO_COUNT 8 /* maximum retry read IO or
>>> flush count */
>>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>>> index 4254db453b2d..63e9ee7ab911 100644
>>> --- a/fs/f2fs/node.c
>>> +++ b/fs/f2fs/node.c
>>> @@ -860,7 +860,9 @@ int f2fs_get_dnode_of_data(struct dnode_of_data *dn,
>>> pgoff_t index, int mode)
>>> set_nid(parent, offset[i - 1], nids[i], i == 1);
>>> f2fs_alloc_nid_done(sbi, nids[i]);
>>> done = true;
>>> - } else if (mode == LOOKUP_NODE_RA && i == level && level > 1) {
>>> + } else if ((mode == LOOKUP_NODE_RA ||
>>> + (mode == LOOKUP_NODE_PRECACHE))
>>> + && i == level && level > 1) {
>>> nfolio[i] = f2fs_get_node_folio_ra(parent, offset[i -
>>> 1]);
>>> if (IS_ERR(nfolio[i])) {
>>> err = PTR_ERR(nfolio[i]);
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