| Message ID | 20210505190104.70112-1-colin.king@canonical.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | scsi: ufs: ufs-exynos: make a const array static, makes object smaller | expand |
On 05/05/2021 15:01, Colin King wrote: > From: Colin Ian King <colin.king@canonical.com> > > Don't populate the const array granularity_tbl on the stack but instead it > static. Makes the object code smaller by 190 bytes: > > Before: > text data bss dec hex filename > 25563 6908 0 32471 7ed7 ./drivers/scsi/ufs/ufs-exynos.o > > After: > text data bss dec hex filename > 25213 7068 0 32281 7e19 ./drivers/scsi/ufs/ufs-exynos.o > > (gcc version 10.3.0) I am not sure what's the benefit here - you moved the code from text to data. In total you decreased the size for this compilation settings (e.g. compiler + optimizations) but that might not be always true, right? This has effect on the code readability - line is longer and reader would think "why this was made static since it is simple one-time const?". Best regards, Krzysztof
On 05/05/2021 20:41, Krzysztof Kozlowski wrote: > On 05/05/2021 15:01, Colin King wrote: >> From: Colin Ian King <colin.king@canonical.com> >> >> Don't populate the const array granularity_tbl on the stack but instead it >> static. Makes the object code smaller by 190 bytes: >> >> Before: >> text data bss dec hex filename >> 25563 6908 0 32471 7ed7 ./drivers/scsi/ufs/ufs-exynos.o >> >> After: >> text data bss dec hex filename >> 25213 7068 0 32281 7e19 ./drivers/scsi/ufs/ufs-exynos.o >> >> (gcc version 10.3.0) > > I am not sure what's the benefit here - you moved the code from text to > data. In total you decreased the size for this compilation settings > (e.g. compiler + optimizations) but that might not be always true, right? It is a marginal saving, but for arrays this size it makes sense to not have to populate the data into the stack before using it and then discarding it. This change essentially replaces quite a lot of instructions that put the data onto the stack so I think it's worth while. > > This has effect on the code readability - line is longer and reader > would think "why this was made static since it is simple one-time const?". > Not sure how to respond to this. If they wonder why it is static const and don't know why then one would hope they look it up in K&R and familiarize themselves with C. It's not so subtle. Colin > > Best regards, > Krzysztof >
Colin, > Don't populate the const array granularity_tbl on the stack but instead it > static. Makes the object code smaller by 190 bytes: Applied to 5.14/scsi-staging, thanks!
On Wed, 5 May 2021 20:01:04 +0100, Colin King wrote: > Don't populate the const array granularity_tbl on the stack but instead it > static. Makes the object code smaller by 190 bytes: > > Before: > text data bss dec hex filename > 25563 6908 0 32471 7ed7 ./drivers/scsi/ufs/ufs-exynos.o > > [...] Applied to 5.14/scsi-queue, thanks! [1/1] scsi: ufs: ufs-exynos: make a const array static, makes object smaller https://git.kernel.org/mkp/scsi/c/5ac3c649f11c
diff --git a/drivers/scsi/ufs/ufs-exynos.c b/drivers/scsi/ufs/ufs-exynos.c index 70647eacf195..f2f342d496c7 100644 --- a/drivers/scsi/ufs/ufs-exynos.c +++ b/drivers/scsi/ufs/ufs-exynos.c @@ -1048,7 +1048,7 @@ static void exynos_ufs_pre_hibern8(struct ufs_hba *hba, u8 enter) exynos_ufs_ungate_clks(ufs); if (ufs->opts & EXYNOS_UFS_OPT_USE_SW_HIBERN8_TIMER) { - const unsigned int granularity_tbl[] = { + static const unsigned int granularity_tbl[] = { 1, 4, 8, 16, 32, 100 }; int h8_time = attr->pa_hibern8time *