2012/9/3, Jan Kara <j...@suse.cz>: > Hello, > > On Fri 31-08-12 12:51:58, Namjae Jeon wrote: >> From: Namjae Jeon <namjae.j...@samsung.com> >> >> While mapping logical blocks of a file to physical blocks on the >> partition, >> everytime UDF read file metadata from the begining which decrease >> preformance. >> The drawback of this scheme is more prominent while reading large files. >> For example, while reading a large file of ~5GB, read speed will >> gradually become less as we near the end of file because of the time >> taken in calculating the corresponding physical block. >> >> This patch implements caching and remembers the location of the last read >> extent. Instead of reading file metadata from begining, start from the >> cached location.
Hi. Jan. > Thanks for the patch. I like this much better than the previous one. Some > comments are below: Thank you~ > >> diff --git a/fs/udf/inode.c b/fs/udf/inode.c >> index 1a0588e..f4cc4e0 100644 >> --- a/fs/udf/inode.c >> +++ b/fs/udf/inode.c >> @@ -357,8 +359,14 @@ static int udf_get_block(struct inode *inode, >> sector_t block, >> if (!phys) >> goto abort; >> >> - if (new) >> + if (new) { >> + unsigned char lshift = inode->i_sb->s_blocksize_bits; >> set_buffer_new(bh_result); >> + if (iinfo->cached_extent.sanity && >> + (iinfo->cached_extent.eblock > (block << lshift))) >> + /* Block allocated for hole, invalidate cache */ >> + udf_clear_extent_cache(iinfo); >> + } >> map_bh(bh_result, inode->i_sb, phys); > Instead of this, you should change inode_getblk() to also use the extent > cache (for initialization of prev_epos when appropriate) and then update > the extent cache to the just found / created extent when the function is > done. Okay, I will check about your suggestion. > >> abort: >> @@ -2132,11 +2144,12 @@ int8_t inode_bmap(struct inode *inode, sector_t >> block, >> struct udf_inode_info *iinfo; >> >> iinfo = UDF_I(inode); >> - pos->offset = 0; >> - pos->block = iinfo->i_location; >> - pos->bh = NULL; >> - *elen = 0; >> - >> + if (!udf_read_extent_cache(inode, bcount, &lbcount, pos)) { >> + pos->offset = 0; >> + pos->block = iinfo->i_location; >> + pos->bh = NULL; >> + } >> + *elen = 0; > There's TAB added here which doesn't make sense. > >> do { >> etype = udf_next_aext(inode, pos, eloc, elen, 1); >> if (etype == -1) { > ... >> @@ -2176,3 +2190,52 @@ long udf_block_map(struct inode *inode, sector_t >> block) >> else >> return ret; >> } >> +int udf_read_extent_cache(struct inode *inode, loff_t bcount, >> + loff_t *lbcount, struct extent_position *pos) >> +{ >> + struct udf_inode_info *iinfo = UDF_I(inode); >> + mutex_lock(&iinfo->i_extent_cache_lock); >> + if ((iinfo->cached_extent.eblock <= bcount) && >> + (iinfo->cached_extent.sanity)) { >> + /* Cache hit */ >> + *lbcount = iinfo->cached_extent.eblock; >> + memcpy(pos, &iinfo->cached_extent.epos, >> + sizeof(struct extent_position)); >> + mutex_unlock(&iinfo->i_extent_cache_lock); >> + return 1; >> + } else >> + udf_clear_extent_cache(iinfo); > It would be less confusing, if udf_read_extent_cache() didn't clear the > cache in case of a miss. Then in udf_update_extent_cache() just clear the > cache if it is still valid. Okay, It is more effective! I will change ~ > >> + >> + mutex_unlock(&iinfo->i_extent_cache_lock); >> + return 0; >> +} >> +void udf_update_extent_cache(struct inode *inode, loff_t estart, >> + struct extent_position *pos) >> +{ >> + struct udf_inode_info *iinfo = UDF_I(inode); >> + mutex_lock(&iinfo->i_extent_cache_lock); >> + if (pos->bh != NULL) >> + /* Increase ref count */ >> + get_bh(pos->bh); >> + memcpy(&iinfo->cached_extent.epos, pos, >> + sizeof(struct extent_position)); >> + iinfo->cached_extent.eblock = estart; >> + iinfo->cached_extent.sanity = 1; >> + switch (iinfo->i_alloc_type) { >> + case ICBTAG_FLAG_AD_SHORT: >> + iinfo->cached_extent.epos.offset -= sizeof(struct short_ad); >> + break; >> + case ICBTAG_FLAG_AD_LONG: >> + iinfo->cached_extent.epos.offset -= sizeof(struct long_ad); >> + } >> + mutex_unlock(&iinfo->i_extent_cache_lock); >> +} >> + >> +void udf_clear_extent_cache(struct udf_inode_info *iinfo) >> +{ >> + if (iinfo->cached_extent.sanity) { >> + brelse(iinfo->cached_extent.epos.bh); >> + memset(&iinfo->cached_extent, 0, sizeof(struct udf_ext_cache)); >> + } >> +} >> + > I think udf_clear_entent_cache() should take i_extent_cache_lock. Or if > you are sure it's not needed, you need a good documentation why. Documentation ? I am a little confusing.. It means udf.txt is in Documentation/filesystem/ ? or comment about clear extent function ? > >> diff --git a/fs/udf/udf_i.h b/fs/udf/udf_i.h >> index bb8309d..ec3878a 100644 >> --- a/fs/udf/udf_i.h >> +++ b/fs/udf/udf_i.h >> @@ -1,6 +1,20 @@ >> #ifndef _UDF_I_H >> #define _UDF_I_H >> >> +struct extent_position { >> + struct buffer_head *bh; >> + uint32_t offset; >> + struct kernel_lb_addr block; >> +}; >> + >> +struct udf_ext_cache { >> + /* Extent position */ >> + struct extent_position epos; >> + /* Start logical block */ >> + loff_t eblock; > Well, this is really in bytes not blocks, isn't it? Then call it like > 'lstart' and add a comment that it's in bytes. Yes, It is in bytes. And I will add comment. > >> + int8_t sanity; > Make this 'bool' and call it 'valid'. That's more common. Okay, I will modify bool. Thanks a lot. Jan! > > Honza > -- > Jan Kara <j...@suse.cz> > SUSE Labs, CR > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/