[PATCH v2 1/3] feat: scale vmpressure window with machine size

[PATCH v2 1/3] feat: scale vmpressure window with machine size

[deepakroag]

Replace the fixed 512-page vmpressure window with a boot-time value
derived from total memory and CPU count, clamped between 128 and 2048 pages.

Signed-off-by: deepakroag <gaikwad.dcg@gmail.com>
---
 mm/vmpressure.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index f053554e5..8925d4ad3 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -33,9 +33,29 @@
  * SWAP_CLUSTER_MAX, it makes sense to use it for the window size as well.
  *
  * TODO: Make the window size depend on machine size, as we do for vmstat
- * thresholds. Currently we set it to 512 pages (2MB for 4KB pages).
+ * thresholds. Scales with CPU count and total memory at boot.
  */
-static const unsigned long vmpressure_win = SWAP_CLUSTER_MAX * 16;
+static unsigned long vmpressure_win;
+
+static unsigned long __init vmpressure_window_size(void)
+{
+	unsigned long win;
+	int mem;
+
+	mem = totalram_pages() >> (27 - PAGE_SHIFT);
+	win = SWAP_CLUSTER_MAX * (unsigned long)fls(num_online_cpus()) *
+	      (1 + fls(mem));
+	win = max(win, SWAP_CLUSTER_MAX * 4UL);
+	win = min(win, SWAP_CLUSTER_MAX * 64UL);
+	return win;
+}
+
+static int __init vmpressure_win_init(void)
+{
+	vmpressure_win = vmpressure_window_size();
+	return 0;
+}
+core_initcall(vmpressure_win_init);
 
 /*
  * These thresholds are used when we account memory pressure through
-- 
Deepak Rao Gaikwad

Re: [PATCH v2 1/3] feat: scale vmpressure window with machine size

[Lorenzo Stoakes (ARM)]

NAK.

I'm not sure what you're doing here but this looks suspiciously like you're
taking somebody else's (previously rejected) work and putting your name to it?

And you're sending a v2 without having sent a v1? What?

You're also getting basic process wrong here. We don't prefix with 'feat'. You
only cc'd key people on 1/3 patches.

There doesn't appear to be a cover letter. You are sending random vmalloc
changes along with this too?

On Thu, Jul 16, 2026 at 05:27:30PM +0530, deepakroag wrote:
> Replace the fixed 512-page vmpressure window with a boot-time value
> derived from total memory and CPU count, clamped between 128 and 2048 pages.

So you're just making stuff up here? Clamp between 128 and 2048 because why not
I guess? And no mention about the rest of the logic?

>
> Signed-off-by: deepakroag <gaikwad.dcg@gmail.com>
> ---

There was already a patch for this in [0] which looks suspiciously close to what
you're doing here (modulo clamping without using a clamp macro),
unacknowledged.

I hope you understand plagiarism is completely unacceptable?

In any case it was rejected then for various reasons, you re-sending the same
idea without crediting that changes nothing.

Cheers, Lorenzo

[0]:https://lore.kernel.org/all/20260227221555.29969-1-mcq@disroot.org/

>  mm/vmpressure.c | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/mm/vmpressure.c b/mm/vmpressure.c
> index f053554e5..8925d4ad3 100644
> --- a/mm/vmpressure.c
> +++ b/mm/vmpressure.c
> @@ -33,9 +33,29 @@
>   * SWAP_CLUSTER_MAX, it makes sense to use it for the window size as well.
>   *
>   * TODO: Make the window size depend on machine size, as we do for vmstat
> - * thresholds. Currently we set it to 512 pages (2MB for 4KB pages).
> + * thresholds. Scales with CPU count and total memory at boot.
>   */
> -static const unsigned long vmpressure_win = SWAP_CLUSTER_MAX * 16;
> +static unsigned long vmpressure_win;
> +
> +static unsigned long __init vmpressure_window_size(void)
> +{
> +	unsigned long win;
> +	int mem;
> +
> +	mem = totalram_pages() >> (27 - PAGE_SHIFT);
> +	win = SWAP_CLUSTER_MAX * (unsigned long)fls(num_online_cpus()) *
> +	      (1 + fls(mem));
> +	win = max(win, SWAP_CLUSTER_MAX * 4UL);
> +	win = min(win, SWAP_CLUSTER_MAX * 64UL);
> +	return win;
> +}
> +
> +static int __init vmpressure_win_init(void)
> +{
> +	vmpressure_win = vmpressure_window_size();
> +	return 0;
> +}
> +core_initcall(vmpressure_win_init);
>
>  /*
>   * These thresholds are used when we account memory pressure through
> --
> Deepak Rao Gaikwad
>

Re: [PATCH v2 1/3] feat: scale vmpressure window with machine size

[deepakroag]

Hi Lorenzo,

Thank you for the review. I withdraw the entire [PATCH v2 0/3] series.

You are right that the vmpressure change closely follows Benjamin Lee
McQueen's earlier rejected thread without proper attribution or an RFC.
That was a serious mistake on my part, and I am sorry for the confusion
and for wasting your time.

I will not resubmit the vmpressure or vrealloc changes. I also
understand that bundling unrelated mm, selftest, and vmalloc work in one
series, using non-kernel subject prefixes, and sending v2 without a
proper v1 review cycle were process errors on my side.

Going forward I will stick to small, original fixes, search lore before
proposing mm changes, and follow the normal RFC/review process for
anything touching vmpressure or vmalloc.

Thank you,
Deepak Rao Gaikwad

[PATCH v2 3/3] feat: grow vrealloc vm_area mappings in place

[deepakroag]

Allocate and map additional pages at the end of an existing vm_area when
vrealloc() grows past mapped pages, falling back to the memcpy path
otherwise.

Use flags (not gfp) in the in-place grow path for kvmalloc_array and
vm_area_alloc_pages.

Signed-off-by: deepakroag <gaikwad.dcg@gmail.com>
---
 mm/vmalloc.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 1afca3568..1eff71240 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4426,8 +4426,56 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align
 		return (void *)p;
 	}
 
+	{
+		unsigned int new_nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
+		unsigned int old_nr_pages = vm->nr_pages;
+
+		if (new_nr_pages > old_nr_pages && !vm_area_page_order(vm) &&
+		    !(vm->flags & (VM_FLUSH_RESET_PERMS | VM_USERMAP)) &&
+		    gfp_has_io_fs(flags)) {
+			unsigned int extra = new_nr_pages - old_nr_pages;
+			unsigned long addr = (unsigned long)kasan_reset_tag(p);
+			struct vmap_node *vn = addr_to_node(addr);
+			struct page **pages;
+			int ret;
+
+			pages = kvmalloc_array(extra, sizeof(struct page *), flags);
+			if (!pages)
+				goto need_realloc;
+
+			if (vm_area_alloc_pages(vmalloc_gfp_adjust(flags, 0), nid,
+						0, extra, pages) != extra) {
+				kvfree(pages);
+				goto need_realloc;
+			}
+
+			spin_lock(&vn->busy.lock);
+			ret = vmap_pages_range(addr + ((unsigned long)old_nr_pages
+						       << PAGE_SHIFT),
+					       addr + ((unsigned long)new_nr_pages
+						       << PAGE_SHIFT),
+					       PAGE_KERNEL, pages, PAGE_SHIFT);
+			spin_unlock(&vn->busy.lock);
+			if (ret < 0) {
+				free_pages_bulk(pages, extra);
+				kvfree(pages);
+				goto need_realloc;
+			}
+
+			memcpy(&vm->pages[old_nr_pages], pages,
+			       extra * sizeof(struct page *));
+			kvfree(pages);
+			vm->nr_pages = new_nr_pages;
+			vm->requested_size = size;
+			kasan_vrealloc(p, old_size, size);
+			if (want_init_on_alloc(flags))
+				memset((void *)p + old_size, 0, size - old_size);
+			return (void *)p;
+		}
+	}
+
 need_realloc:
-	/* TODO: Grow the vm_area, i.e. allocate and map additional pages. */
+	/* Fall back to a fresh vm_area when in-place grow is not possible. */
 	n = __vmalloc_node_noprof(size, align, flags, nid, __builtin_return_address(0));
 
 	if (!n)
-- 
Deepak Rao Gaikwad