On Thu, May 12, 2022 at 1:01 AM Paul Menzel [off-list ref] wrote:

Dear Christoph,


Am 12.05.22 um 08:27 schrieb Christoph Hellwig:

quoted

On Thu, May 12, 2022 at 08:25:28AM +0200, Paul Menzel wrote:

quoted

quoted

Am 12.05.22 um 08:19 schrieb Christoph Hellwig:

quoted

Use the %pg format specifier to save on stack consuption and code size.

consu*m*ption

Did you do any measurements?

Each BDEVNAME_SIZE array consumes 32 bytes on the stack, and they are
gone now without any additional stack usage elsewhere.

Understood.

For comparing the code size, out of curiosity, I built `drivers/md` from
md-next, commit 74fe94569da7 (md: protect md_unregister_thread from
reentrancy), without and with your patch with gcc 11.1.0, and got:

$ diff -u <(cd drivers/md-before/ && du -a | sort -k2) <(cd drivers/md/
&& du -a | sort -k2)
--- /dev/fd/63  2022-05-12 09:51:23.354107016 +0200
+++ /dev/fd/62  2022-05-12 09:51:23.355107064 +0200
@@ -1,4 +1,4 @@
-11064  .
+11052  .
  4      ./.built-in.a.cmd
  48     ./.dm-bio-prison-v1.o.cmd
  20     ./.dm-bio-prison-v1.o.d
@@ -287,7 +287,7 @@
  24     ./md-multipath.o
  260    ./md.c
  28     ./md.h
-308    ./md.o
+304    ./md.o
  4      ./modules.order
  1380   ./persistent-data
  48     ./persistent-data/.dm-array.o.cmd
@@ -356,7 +356,7 @@
  148    ./raid10.c
  8      ./raid10.h
  4      ./raid10.mod
-108    ./raid10.o
+104    ./raid10.o
  88     ./raid5-cache.c
  76     ./raid5-cache.o
  8      ./raid5-log.h
@@ -364,4 +364,4 @@
  48     ./raid5-ppl.o
  252    ./raid5.c
  32     ./raid5.h
-212    ./raid5.o
+208    ./raid5.o

Kind regards,

Paul

Applied to md-next. Thanks!

Song