On 2026/2/25 00:02, Matthew Lear wrote:
Hi Gao Xiang,
Thank you for the quick reply.
Is there scope to increase the default block size ceiling of mkfs.erofs
to 16K (or perhaps increase it to 16K for aarch64 compilations)?
I think the reasonable maximum block size for EROFS should be no
more than 64k.
I think we could consider set the MAX_BLOCK_SIZE to 64k for
aarch64, but leave it to the page size if `-b` is unspecified.
Would you mind submitting a patch for this (checking the target
arch, if aarch64, set MAX_BLOCK_SIZE to 64k instead) since I've
already had a bunch of other stuffs.
A change in configure.ac to do this looks straight-forward enough (I
think), but there may be justified concerns about the knock-on effects,
particularly as MAX_BLOCK_SIZE is used in various arrays. With 16K (4x
today), these would all increase quite a bit:
lib/liberofs_cache.h: struct list_head watermeter[META +
1][2][EROFS_MAX_BLOCK_SIZE];
lib/namei.c: char buf[EROFS_MAX_BLOCK_SIZE];
lib/dir.c: char buf[EROFS_MAX_BLOCK_SIZE];
lib/data.c: u8 buf[EROFS_MAX_BLOCK_SIZE];
lib/super.c: u8 data[EROFS_MAX_BLOCK_SIZE];
With 64K, the memory footprint would be significantly larger.
What do you think?
I understand your concern although I think they are just
for temporary use, and 64k is still not too huge and
the userspace stack is less worried.
Or how about just use max(PAGE_SIZE, 16k) instead for
aarch64? then you will get 16k for most of the time
unless PAGE_SIZE > 16k.
Thanks,
Gao Xiang
-- Matt
