doc: clarify what --alloc-size does

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 4201e2e946f0a4594eb04f778eee575122696536..4fef1504a410a205c95c7c85b489f0068bceb1a5 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -222,8 +222,8 @@ Command line options
 
 .. option:: --alloc-size=kb
 
-       Set the internal smalloc pool size to `kb` in KiB.  The
-       ``--alloc-size`` switch allows one to use a larger pool size for smalloc.
+       Allocate additional internal smalloc pools of size `kb` in KiB.  The
+       ``--alloc-size`` option increases shared memory set aside for use by fio.
        If running large jobs with randommap enabled, fio can run out of memory.
        Smalloc is an internal allocator for shared structures from a fixed size
        memory pool and can grow to 16 pools. The pool size defaults to 16MiB.
@@ -2033,6 +2033,12 @@ with the caveat that when used on the command line, they must come after the
        map and release for each IO. This is more efficient, and reduces the
        IO latency as well.
 
+.. option:: registerfiles : [io_uring]
+       With this option, fio registers the set of files being used with the
+       kernel. This avoids the overhead of managing file counts in the kernel,
+       making the submission and completion part more lightweight. Required
+       for the below :option:`sqthread_poll` option.
+
 .. option:: sqthread_poll : [io_uring]
 
        Normally fio will submit IO by issuing a system call to notify the