| Message ID | 20230116030850.20260-1-qixiaoyu1@xiaomi.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [f2fs-dev,1/2,v2] f2fs: fix wrong calculation of block age | expand |
On 2023/1/16 11:08, qixiaoyu1 wrote: > Currently we wrongly calculate the new block age to > old * LAST_AGE_WEIGHT / 100. > > Fix it to new * (100 - LAST_AGE_WEIGHT) / 100 > + old * LAST_AGE_WEIGHT / 100. > > Signed-off-by: qixiaoyu1 <qixiaoyu1@xiaomi.com> > Signed-off-by: xiongping1 <xiongping1@xiaomi.com> > --- > Change log v1 -> v2: > - fix udiv > > fs/f2fs/extent_cache.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c > index 342af24b2f8c..ad5533f178fd 100644 > --- a/fs/f2fs/extent_cache.c > +++ b/fs/f2fs/extent_cache.c > @@ -874,11 +874,8 @@ void f2fs_update_read_extent_tree_range_compressed(struct inode *inode, > static unsigned long long __calculate_block_age(unsigned long long new, > unsigned long long old) > { > - unsigned long long diff; > - > - diff = (new >= old) ? new - (new - old) : new + (old - new); > - > - return div_u64(diff * LAST_AGE_WEIGHT, 100); > + return div_u64(new, 100) * (100 - LAST_AGE_WEIGHT) > + + div_u64(old, 100) * LAST_AGE_WEIGHT; How about updating as below to avoid lossing accuracy if new is less than 100? return div_u64(new * (100 - LAST_AGE_WEIGHT), 100) + div_u64(old * LAST_AGE_WEIGHT, 100); Thanks, > } > > /* This returns a new age and allocated blocks in ei */
On Sat, Jan 28, 2023 at 11:35:34AM +0800, Chao Yu wrote: > On 2023/1/16 11:08, qixiaoyu1 wrote: > > Currently we wrongly calculate the new block age to > > old * LAST_AGE_WEIGHT / 100. > > > > Fix it to new * (100 - LAST_AGE_WEIGHT) / 100 > > + old * LAST_AGE_WEIGHT / 100. > > > > Signed-off-by: qixiaoyu1 <qixiaoyu1@xiaomi.com> > > Signed-off-by: xiongping1 <xiongping1@xiaomi.com> > > --- > > Change log v1 -> v2: > > - fix udiv > > > > fs/f2fs/extent_cache.c | 7 ++----- > > 1 file changed, 2 insertions(+), 5 deletions(-) > > > > diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c > > index 342af24b2f8c..ad5533f178fd 100644 > > --- a/fs/f2fs/extent_cache.c > > +++ b/fs/f2fs/extent_cache.c > > @@ -874,11 +874,8 @@ void f2fs_update_read_extent_tree_range_compressed(struct inode *inode, > > static unsigned long long __calculate_block_age(unsigned long long new, > > unsigned long long old) > > { > > - unsigned long long diff; > > - > > - diff = (new >= old) ? new - (new - old) : new + (old - new); > > - > > - return div_u64(diff * LAST_AGE_WEIGHT, 100); > > + return div_u64(new, 100) * (100 - LAST_AGE_WEIGHT) > > + + div_u64(old, 100) * LAST_AGE_WEIGHT; > > How about updating as below to avoid lossing accuracy if new is less than 100? > > return div_u64(new * (100 - LAST_AGE_WEIGHT), 100) + > div_u64(old * LAST_AGE_WEIGHT, 100); > > Thanks, > We want to avoid overflow by doing the division first. To keep the accuracy, how about updating as below: res = div_u64_rem(new, 100, &rem_new) * (100 - LAST_AGE_WEIGHT) + div_u64_rem(old, 100, &rem_old) * LAST_AGE_WEIGHT; res += rem_new * (100 - LAST_AGE_WEIGHT) / 100 + rem_old * LAST_AGE_WEIGHT / 100; return res; Thanks, > > } > > /* This returns a new age and allocated blocks in ei */
> > > > How about updating as below to avoid lossing accuracy if new is less than 100? > > > > return div_u64(new * (100 - LAST_AGE_WEIGHT), 100) + > > div_u64(old * LAST_AGE_WEIGHT, 100); > > > > Thanks, > > > > We want to avoid overflow by doing the division first. To keep the accuracy, how > about updating as below: > > res = div_u64_rem(new, 100, &rem_new) * (100 - LAST_AGE_WEIGHT) > + div_u64_rem(old, 100, &rem_old) * LAST_AGE_WEIGHT; > res += rem_new * (100 - LAST_AGE_WEIGHT) / 100 + rem_old * LAST_AGE_WEIGHT / 100; > return res; > > Thanks, > Friendly ping > > > } > > > /* This returns a new age and allocated blocks in ei */
On 2023/2/1 20:23, qixiaoyu wrote: >>> >>> How about updating as below to avoid lossing accuracy if new is less than 100? >>> >>> return div_u64(new * (100 - LAST_AGE_WEIGHT), 100) + >>> div_u64(old * LAST_AGE_WEIGHT, 100); >>> >>> Thanks, >>> >> >> We want to avoid overflow by doing the division first. To keep the accuracy, how Alright, >> about updating as below: >> >> res = div_u64_rem(new, 100, &rem_new) * (100 - LAST_AGE_WEIGHT) >> + div_u64_rem(old, 100, &rem_old) * LAST_AGE_WEIGHT; >> res += rem_new * (100 - LAST_AGE_WEIGHT) / 100 + rem_old * LAST_AGE_WEIGHT / 100; >> return res; if (rem_new) res += rem_new * (100 - LAST_AGE_WEIGHT) / 100; if (rem_old) res += rem_old * LAST_AGE_WEIGHT / 100; Otherwise, it looks fine to me. :) Thanks, >> >> Thanks, >> > > Friendly ping > >>>> } >>>> /* This returns a new age and allocated blocks in ei */
On Wed, Feb 01, 2023 at 08:57:33PM +0800, Chao Yu wrote: > On 2023/2/1 20:23, qixiaoyu wrote: > > > > > > > > How about updating as below to avoid lossing accuracy if new is less than 100? > > > > > > > > return div_u64(new * (100 - LAST_AGE_WEIGHT), 100) + > > > > div_u64(old * LAST_AGE_WEIGHT, 100); > > > > > > > > Thanks, > > > > > > > > > > We want to avoid overflow by doing the division first. To keep the accuracy, how > > Alright, > > > > about updating as below: > > > > > > res = div_u64_rem(new, 100, &rem_new) * (100 - LAST_AGE_WEIGHT) > > > + div_u64_rem(old, 100, &rem_old) * LAST_AGE_WEIGHT; > > > res += rem_new * (100 - LAST_AGE_WEIGHT) / 100 + rem_old * LAST_AGE_WEIGHT / 100; > > > return res; > > if (rem_new) > res += rem_new * (100 - LAST_AGE_WEIGHT) / 100; > if (rem_old) > res += rem_old * LAST_AGE_WEIGHT / 100; > > Otherwise, it looks fine to me. :) > > Thanks, > Thank you! I will update v3 soon :) > > > > > > Thanks, > > > > > > > Friendly ping > > > > > > > } > > > > > /* This returns a new age and allocated blocks in ei */
diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c index 342af24b2f8c..ad5533f178fd 100644 --- a/fs/f2fs/extent_cache.c +++ b/fs/f2fs/extent_cache.c @@ -874,11 +874,8 @@ void f2fs_update_read_extent_tree_range_compressed(struct inode *inode, static unsigned long long __calculate_block_age(unsigned long long new, unsigned long long old) { - unsigned long long diff; - - diff = (new >= old) ? new - (new - old) : new + (old - new); - - return div_u64(diff * LAST_AGE_WEIGHT, 100); + return div_u64(new, 100) * (100 - LAST_AGE_WEIGHT) + + div_u64(old, 100) * LAST_AGE_WEIGHT; } /* This returns a new age and allocated blocks in ei */
Currently we wrongly calculate the new block age to old * LAST_AGE_WEIGHT / 100. Fix it to new * (100 - LAST_AGE_WEIGHT) / 100 + old * LAST_AGE_WEIGHT / 100. Signed-off-by: qixiaoyu1 <qixiaoyu1@xiaomi.com> Signed-off-by: xiongping1 <xiongping1@xiaomi.com> --- Change log v1 -> v2: - fix udiv fs/f2fs/extent_cache.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)