On Tue, Mar 18, 2025 at 05:43:41PM +0000, Ryan Roberts wrote:
create_pagecache_thp_and_fd() was previously writing a file sized at twice the PMD size by making a per-byte write syscall. This was quite slow when the PMD size is 4M, but completely intolerable for 32M (PMD size for arm64's 16K page size), and 512M (PMD size for arm64's 64K page size).
The byte pattern has a 256 byte period, so let's create a 1K buffer and fill it with exactly 4 periods. Then we can write the buffer as many times as is required to fill the file. This makes things much more tolerable.
The test now passes for 16K page size. It still fails for 64K page size because MAX_PAGECACHE_ORDER is too small for 512M folio size (I think).
Signed-off-by: Ryan Roberts ryan.roberts@arm.com
Acked-by: Peter Xu peterx@redhat.com