Note: This bug is displayed in read-only format because the product is no longer active in Red Hat Bugzilla.

RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.

+++ This bug was initially created as a clone of Bug #820019 +++

When we extended nfsd's maximum IO size to 1MB, the servers configured with lots of nfsd threads started failing to create them all, because more memory was then required per thread.

For the short term we decided to document the change and allow people to manually adjust the maximum IO size.

However as noticed at
https://bugzilla.redhat.com/show_bug.cgi?id=765751#c21

we'd get a more reasonable defaults on 32-bit servers if the heuristic used to choose a default maximum IO size was based on the amount of low memory available instead of on the total amount of RAM available.

Patches doing this have since gone upstream: 508f92275624fc755104b17945bdc822936f1918 "nfsd: fix default iosize calculation on 32bit" and 87b0fc7deb5feccf93b022f6a976e8441152dbb2 "nfsd: cleanup setting of default max_block_size".

This request was evaluated by Red Hat Product Management for
inclusion in a Red Hat Enterprise Linux release.  Product
Management has requested further review of this request by
Red Hat Engineering, for potential inclusion in a Red Hat
Enterprise Linux release for currently deployed products.
This request is not yet committed for inclusion in a release.

This can decrease the maximum IO size on upgrade.  A few upstream users have reported problems when the upgrade without remounting clients: in that case, clients will continue trying to use the old (larger) IO size but the server will drop those (now too-large) requests.

We could do something more sophisticated.

For now let's leave the rhel6 behavior alone.  We can reconsider if it turns out to be a problem for someone.