Date: Thu, 15 May 2025 14:28:05 GMT From: Olivier Certner <olce@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: bf8890c84bac - main - vfs: vntblinit(): Rework comments on the computation of 'kern.maxvnodes' Message-ID: <202505151428.54FES5ov059319@gitrepo.freebsd.org>
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The branch main has been updated by olce: URL: https://cgit.FreeBSD.org/src/commit/?id=bf8890c84bacd8b1acebb2cb9a0944b1bb102b68 commit bf8890c84bacd8b1acebb2cb9a0944b1bb102b68 Author: Olivier Certner <olce@FreeBSD.org> AuthorDate: 2025-05-12 11:20:01 +0000 Commit: Olivier Certner <olce@FreeBSD.org> CommitDate: 2025-05-15 14:27:42 +0000 vfs: vntblinit(): Rework comments on the computation of 'kern.maxvnodes' Remove the parts that describe what is already in the code formula. Add hints about which of 'physvnodes'/'virtvnodes' takes precedence, and when 'desiredvnodes' becomes smaller than 'maxfiles'. These were both computed analytically and verified experimentally. Reviewed by: kib (older version) MFC after: 3 days Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D50310 --- sys/kern/vfs_subr.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c index 5fdd4b6c2474..769586ad0d6b 100644 --- a/sys/kern/vfs_subr.c +++ b/sys/kern/vfs_subr.c @@ -757,15 +757,15 @@ vntblinit(void *dummy __unused) int cpu, physvnodes, virtvnodes; /* - * Desiredvnodes is a function of the physical memory size and the - * kernel's heap size. Generally speaking, it scales with the - * physical memory size. The ratio of desiredvnodes to the physical - * memory size is 1:16 until desiredvnodes exceeds 98,304. - * Thereafter, the - * marginal ratio of desiredvnodes to the physical memory size is - * 1:64. However, desiredvnodes is limited by the kernel's heap - * size. The memory required by desiredvnodes vnodes and vm objects - * must not exceed 1/10th of the kernel's heap size. + * 'desiredvnodes' is the minimum of a function of the physical memory + * size and another of the kernel heap size (UMA limit, a portion of the + * KVA). + * + * Currently, on 64-bit platforms, 'desiredvnodes' is set to + * 'virtvnodes' up to a physical memory cutoff of ~1674MB, after which + * 'physvnodes' applies instead. With the current automatic tuning for + * 'maxfiles' (32 files/MB), 'desiredvnodes' becomes smaller than it at + * ~5136MB. */ physvnodes = maxproc + pgtok(vm_cnt.v_page_count) / 64 + 3 * min(98304 * 16, pgtok(vm_cnt.v_page_count)) / 64;
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