linux-kernel - RE: [PATCH v8 07/15] x86/sgx: Expose sgx_reclaim

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Date: Tue, 30 Jan 2024 15:39:44 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: Haitao Huang <haitao.huang@...ux.intel.com>, "jarkko@...nel.org"
	<jarkko@...nel.org>, "dave.hansen@...ux.intel.com"
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Subject: RE: [PATCH v8 07/15] x86/sgx: Expose sgx_reclaim_pages() for cgroup

> + * @lru:	The LRU from which pages are reclaimed.
> + * @nr_to_scan: Pointer to the target number of pages to scan, must be less
> than
> + *		SGX_NR_TO_SCAN.
> + * Return:	Number of pages reclaimed.
>   */
> -static void sgx_reclaim_pages(void)
> +unsigned int sgx_reclaim_pages(struct sgx_epc_lru_list *lru, unsigned
> +int *nr_to_scan)

Since the function is now returning the number of reclaimed pages, why do you need to make the @nr_to_scan as pointer?

Cannot the caller just adjust @nr_to_scan when calling this function based on how many pages have reclaimed?

I am not even sure whether you need @nr_to_scan at all because as we discussed I think it's just extremely rare you need to pass "< SGX_NR_TO_SCAN" to this function.

Even if you need, you can always choose to try to reclaim SGX_NR_TO_SCAN pages.

[...]

> 
> +static void sgx_reclaim_pages_global(void) {
> +	unsigned int nr_to_scan = SGX_NR_TO_SCAN;
> +
> +	sgx_reclaim_pages(&sgx_global_lru, &nr_to_scan); }
> +

I think this function doesn't look sane at all when you have @nr_to_scan being a pointer?

I am also not sure whether this function is needed -- if we don't add @nr_to_scan to sgx_reclaim_pages(), then this function is basically:

	sgx_reclaim_pages(&sgx_global_lru);